Capping off a brutal week of frigid conditions and subzero wind chills, residents across much of the country on Friday were still experiencing some of the coldest temperatures in years — with southern states getting a rare icy blast.

Peak temperatures from the Northeast to the Midwest were slated to range from single digits to the 30s, and forecasters said freezing air temperatures and the chance of precipitation could mean snow in both regions.

"This is actually quite an impressive mass of cold air," Richard Castro, a meteorologist at the National Weather Service told NBCChicago.com.

By mid-afternoon on Friday, Pennsylvania was feeling the first of a "widespread storm, impacting the entire state," said state's transportation department spokesman Steve Chizmar.

Snow was falling over most of the state, and forecasters predicted a total of 1 to 4 inches through Saturday morning, while transportation department crews stayed busy plowing and salting the roads.

Hundreds of schools in the state dismissed classes early Friday.

Only a light dusting, if any accumulation, was expected in New York City, where real-feel temperatures were below zero Friday morning, NBCNewYork.com reported.

Slideshow: Deep Freeze

Timothy A. Clary / AFP - Getty Images

A man photographs the fountain at Bryant Park in New York on Friday as the arctic air has turned the fountain into an ice sculpture.

Launch slideshow

In the Midwest, one of the first snowfalls of the season in Chicago created a few slick spots on the roads Friday morning, causing at least a dozen accidents, including an eight-vehicle crash, NBCChicago.com reported. Only minor injuries had been reported.

Though little snow accumulated it was still record breaking. The 1.1 inches recorded Friday morning broke the city’s 335-day stretch of no more than an inch of snow accumulation in one day.

The National Weather Service had winter weather advisories in effect for the eastern seaboard from North Carolina to southern New Jersey, and issued blizzard warnings for northern Georgia.

Parts of Kentucky were reporting as much as half inch of ice accumulation, Weather.com reported. Slick roads in the southeast of the state were making driving hazardous, causing more than 100 accidents in Pulaski County alone, it said.

Tennessee was also slick with ice in the east, and reported some power outages, while freezing rain caused a number of school systems in central and southern Kentucky to cancel classes, according to WLEX-TV.

Because cold temperatures can be dangerous, officials advised residents to heed cold-weather tips, including wearing gloves, wearing a mouth covering to protect the lungs from bitter cold air, layering loose-fitting, warm clothing and wearing a hat to retain body heat.

Animal advocates also urged pet owners to only take elderly dogs, puppies and short-haired dogs outside when it is absolutely necessary. If a dog whines frequently or keeps lifting its paws up while on a walk, it may need boots. Cat owners should keep their animals inside at all times in such bitter cold, NBCChicago.com reported.

The forecast for next week called for some relief from the arctic temperatures of late, beginning with sunny skies and temperatures hitting the mid-40s to 50s by the middle of the week. 

Kari Huus, NBC Staff Writer, contributed to this report.

Courtesy NOAA Visualization Lab

NOAA scientists say the globally-averaged temperature last month, tied with the September record high set in 2005.

If you thought September felt a bit warmer than usual, you weren't alone.

Scientists with the National Oceanic and Atmospheric Administration (NOAA) said Monday that last month tied a 2005 record for the warmest September on record worldwide. These numbers have been tracked since 1880. September's combined average temperature over land and ocean around the world was 60.21 degrees Fahrenheit -- 1.21 degrees over the 20th century average.

The heat was most notable in parts of Russia, Japan, Australia, Argentina, Paraguay, Canada and Greenland. In the United States, September was only the 23rd hottest, The Associated Press reported.

The scientists also noted that September "also marked the 36th consecutive September and 331st consecutive month with a global temperature above the 20th century average."

Records such as this are seemingly being set at a greater rate than they used to be, according to Professor Jonathan E. Martin, chair of atmospheric and oceanic sciences at the University of Wisconsin-Madison. Martin says greenhouse gases are changing the composition of the atmosphere.

"One of the consequences of that is an easier time hurdling past high temperature records," Martin told NBC News, acknowledging that global warming could be at play.

With a September average of 1.39 million square miles, Arctic sea ice also reached its all-time lowest daily extent on record on Sept. 16. Martin speculated that there is a "very strong possibility" that this increased water exposure to the air could be affecting temperatures.

Related: Arctic sea ice reaches new low

The situation was different in the Antarctic, where sea ice actually reached its all-time highest daily extent record on Sept. 26.

Deke Arndt, chief of the climate monitoring branch at NOAA's National Climatic Data Center, said 2012 so far currently clocks in as eighth warmest year on record. Unless there are exceptionally high temperatures the rest of the year, 2005 and 2010 will likely continue holding the title for hottest years on record, he added.

The Associated Press contributed to this story.

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With less than three months left this year, it's looking increasingly likely that 2012 will go down as the warmest year on record in the continental United States.

January-September was already the warmest first nine months, according to temperature data released Tuesday by the National Climatic Data Center.

Moreover, six of eight scenarios charted by the center have 2012 ending warmer than any other year in records that go back to 1895. The only scenarios where that would not happen are if the last quarter is among the 10 coldest on record.

Last month was the 23rd warmest September on record and, more significantly, marked "the 16th consecutive month with above-average temperatures for the Lower 48," the center said in its monthly State of the Climate Report.

January-September temperatures averaged 59.8 degrees Fahrenheit -- 3.8 degrees F above the 20th-century average.

This year has already seen the warmest March and July on record, and, except for September, every other month was in the top 20 warmest, weather.com noted.

Looking ahead, the U.S. Climate Prediction Center last month posted its three-month outlook, citing "enhanced chances for above normal temperatures from the Southwest through the Great Plains to the Northeast."

Weather.com meteorologist Nick Wiltgen noted that only eight of the past 117 years have had an October-December cold enough to drag the U.S. average in 2012 below the "warmest year" record now shared by 2006 and 1998.

In September, Wiltgen calculated that through August "the odds of not surpassing the warmest year on record are about 13 percent."

Now, he tweeted on Tuesday, those odds are about 7 percent.

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Temperatures across the Northeast approached triple digits Wednesday, with some areas breaking their June 20 records, just as summer officially began on the longest day of the year.

NBCNewYork.com reported that new June 20 records included: New York City's LaGuardia Airport at 98 degrees (previous record was 96 in 1953); JFK Airport at 94 degrees (topping 93 in 1955); and Newark, N.J., at 98 (topping 97 in 1953).

Temperatures were 10 to 20 degrees above average across the region and the humidity made it feel even hotter.

In New York City's Central Park, when the temperature hit 93 the humidity made it feel like 97. In Boston, it was 93 but  felt like 100. 

Several people were treated for heat exhaustion at a high school graduation in North Bergen, N.J., and taken to a hospital, The Record of Bergen County reported. Ambulances were on standby at the event, which was held outside to accommodate about 5,000 people, said Capt. Gerald Sanzari of the North Bergen Police Department.

In Howell, N.J., school officials made Wednesday the last day of the school year instead of Thursday, citing the heat. And at nearby Wall High School, people attending the graduation ceremony will be able to watch a remote broadcast inside the air-conditioned building. 

Weather.com posted these temps for 3:45 p.m. ET on Wednesday.

Sweltering heat also persisted farther to the west in the Great Lakes and Ohio Valley, including Chicago, Ill., Detroit, Mich., Cleveland, Ohio, and Louisville, Ky.

Health officials warned residents to drink water, stay out of the sun and in air conditioning, and to check on elderly neighbors and pets. For those without air conditioning, "cooling centers" were set up in public buildings in dozens of cities.

New York City's 1.1 million public school students are still in session for another week, and just 64 percent of classrooms are air-conditioned.

Students were being advised to wear light clothing and drink plenty of water, and schools have been told to limit outdoor playtime, city Education Department spokeswoman Marge Feinberg said.

In Brooklyn, street vendor James Martin said his family's sixth-floor apartment in Coney Island has no air conditioning and can get really hot. But "we open the front door and all the windows, and we get a nice breeze," he said.

Slideshow: Summertime living

Arif Ali / AFP - Getty Images

Celebrating the warm summer months, as schools let out and the cooling off begins

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Buffalo and Rochester, N.Y., opened several spray parks on Tuesday to help residents cool off as hot, muggy weather settled in. Buffalo, which will only be in the mid- to high-80s on Wednesday and Thursday, doesn't normally open its 11 splash pads until July 1.

PhotoBlog: Record high temperatures to greet summer solstice

In a rare bending of the rules, the Metro in Washington, D.C., said passengers on Wednesday and Thursday would be allowed to drink water, an exception to their no-drinks policy.

The National Weather Service said the temperature at Washington National Airport was 95 degrees just before 2 p.m., though it felt like 99.

Moderate relief from the high mercury should come this weekend.

The Associated Press contributed to this report.

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Ed Andrieski / AP

Fire burns through trees in Poudre Canyon northwest of Fort Collins, Colo., on Thursday.

Updated at 11:24 p.m. ET: Much of the U.S. can expect a summer with temperatures above average and significant wildfire potential, government forecasters warned just as folks in some parts were already feeling the heat: dozens in Colorado fled their homes on Thursday due to a fast-growing fire near Fort Collins, while a historic Arizona mining town remained evacuated as a nearby fire continued to spread. 

"You may see a pretty significant wildfire season developing" across the West, Greg Carbin of the U.S. Storm Prediction Center told reporters. "To see fires to the extent that they are this early isn't a good sign."

"Strong signals" exist especially for the Southwest in terms of a hot summer, added Jon Gottschalck, a forecaster at the U.S. Climate Prediction Center.

The CPC also published a map showing more than two-thirds of the continental U.S. as likely facing a summer with above normal temperatures -- from inland California all the way east to Florida and as far up as the Mid-Atlantic region.

NOAA

The cyclical La Nina weather pattern, while having dissipated last month, left behind dry soils across much of the country, which makes for less moisture in the air and warmer temperatures, the forecasters said.

Dry soils, and winds that kicked in, have helped spread wildfires in Arizona and Colorado this week.

U.S. Forest Service officials said a blaze about 20 miles northwest of Fort Collins grew from about 1.5 square miles to more than 11 square miles Thursday amid erratic winds gusts of up to 50 mph.

Authorities ordered mandatory evacuations of about 80 homes near Poudre Canyon earlier in the day, even going door to door to issue warnings.

Residents of about 65 of those homes were allowed to return by early evening, with instructions to be ready to leave again if conditions change.

The fire was approaching the city of Greeley's Milton Seaman Reservoir on Thursday night, but city officials said Greeley's water supply hasn't been affected.

Story: Steep terrain makes Colorado fire a tough one

Strong gusts have also fanned a fire in northern Arizona that earlier this week forced 350 residents of Crown King to flee.

Three wildfires in other parts of the state continue to burn as well, but no structures are threatened.

Strong wind gusts are expected Friday as well.

"High-end critical conditions will quickly develop by late morning to early afternoon across the Southwest," the National Weather service said in an alert.

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The temperature analysis released by the U.S. government each month usually isn't all that riveting, but the one that came out Monday is a doozy -- and not just for weather wonks. Highlights for the contiguous U.S. (excluding Alaska and Hawaii) include:

• Last month was the warmest March on record (records go back to 1895) at 51.1 degrees; this is 8.6 degrees above the 20th century average, according to the National Oceanic and Atmospheric Administration.
• January-March was the warmest first quarter on record; the average temperature of 42 degrees was 6 degrees above average.
• April 2011-March 2012 was the warmest stretch of those 12 months on record; at 55.4 degrees, that period was 2.6 degrees above average.
• In March, 15,292 records were broken for warmth; 7,775 were new daytime highs in cities across the country and 7,517 were new nighttime highs.

For Jake Crouch, a NOAA climate scientist who authored the State of the Climate report, last month will be memorable. While the previous record was just .57 degrees cooler, the year it was set, 1910, was itself an anomaly.

Comparing March to the longterm average and seeing an 8.6 degree spread, he added, "that's huge."

The average temperature of 51.1 degrees for the month was nearly 15 degrees warmer than the coldest March on record: 36.5 degrees, a mark set in 1965.

Chris Dolce, a Weather Channel meteorologist who analyzed the report, was impressed with how widespread the warmth was.

"What is so amazing to me is that 25 states had their warmest March on record," he told msnbc.com. "In addition, another 15 states had a top ten warmest March.  Add the two numbers together and that makes a mind-boggling 40 states that had a March that was among their warmest on record."

An exception to the warm March was Alaska. While not included in the contiguous U.S. average, its March ranked as the 10th coolest on record.

The first quarter warmth also meant several dozen cities saw their warmest January-March on record -- among them New York City and Washington, D.C. Click here for a NOAA list.

So what made for a warm March and first quarter for the contiguous U.S.? Crouch cited the cyclical weather pattern La Nina, which has been weakening but is still around, and changes in Arctic and Atlantic weather patterns that in the previous two winters had actually helped set cold records.

NOAA

States with 118 mean that they saw their warmest year in 118 years of records.

The Arctic pattern, in particular, was "a complete flip," said Crouch, and that kept the jet stream, as well as cold air, farther north than normal in winter and allowed warmer temperatures in from the Gulf of Mexico.

Is manmade warming from burning fossil fuels a factor? 

"There are a lot of factors and it's hard to pinpoint one particular thing," Crouch told msnbc.com, "but this is the kind of thing we'd expect with climate change."

Indeed, for the entire globe, neither March nor the first quarter are likely to set records. Final data aren't out yet, but January-February global temperatures were the 20th warmest, NOAA said.

Still, other NOAA analysts have started trying to assign a value to how much greenhouse gases might be impacting temperatures.

In a report on the "Meteorological March Madness" of last month, the analysts noted that while most of the warmth should be attributed to random weather factors, greenhouse gases "likely contributed on the order of 5% to 10% of the magnitude of the heat wave during 12-23 March."

Slideshow: Spring is in the air!

An early spring coaxes the birds, bees, flowers and humans to come out from winter hibernation.

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Moreover, they concluded, "the probability of heat waves is growing as GHG-induced warming continues to progress. But there is always the randomness."

Stu Ostro, a senior Weather Channel meteorologist, told msnbc.com that the bigger picture isn't promising.

"It's not only what happened in March in North America," he said, "it's the context: the extremity of this extraordinary early-season heat in the U.S. and southern Canada, plus Norway and Scotland breaking their March high temperature records; Texas and Oklahoma in 2011 having their hottest summer on record, even hotter than during the Dust Bowl; the off-the-charts 2010 Russia heat wave along with approximately 20 countries setting high temperature records that summer; and Canada having its warmest winter and year on record in 2010."

"All of this happening with such frequency," he added, "provides overwhelmingly convincing evidence that the overall increased warmth is making the atmosphere more conducive to these sorts of heat extremes."

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Susan Walsh / AP

The recent warm spell across much of the U.S. has included Washington, D.C., where it was 80 degrees on Thursday -- perfect weather for recreating near the Washington Monument.

So now that March feels like May in much of the U.S., what's May going to feel like? The East Coast and South can expect above-normal temperatures, federal forecasters announced Thursday -- a day when Atlanta and Chicago were among the cities that posted new daily highs.

After a brief cooling, the warm spell should continue through the rest of March, especially in the East, and into early summer across the South as well, said Ed O'Lenic, chief of operations at the U.S. Climate Prediction Center.

"It's warming up mighty early," he added.

Signs of a premature spring range from early cherry blossoms in Washington, D.C., to farmers preparing to plant.

"This warm weather will advance crops beyond where they normally are," Reuters quoted meteorologist Joel Burgio of Telvent DTN as saying.

Wheat in the South was ahead of normal, Burgio said, fruit trees are blooming early in the Southeast, and Midwest farmers will be lured into starting spring field work earlier than usual.

"The concern is that if a sudden change to colder weather comes after this very warm interlude, then you could have some crop problems," he said.

But the Climate Prediction Center wasn't expecting that. "Above-average temperatures this spring are most likely from the Desert Southwest through the central and southern Great Plains, the Great Lakes, and the Eastern U.S.," the center said of its three-month outlook, "while the Pacific Northwest and Alaska are favored to be cooler than average."

This week, dozens of cities have seen temperatures above 80 degrees and much of the region has been 30 degrees warmer than normal.

On Thursday, Atlanta saw 82 degrees Fahrenheit, a degree warmer than its previous record for a March 15 back in 1973. Chicago broke its record with 77 degrees, 3 more than in 1995. 

On Wednesday, 307 sites across the country -- the vast majority in the Midwest -- broke their record for the warmest March 14. Ninety-three tied their record.

The same was in store for the rest of the week as well, though a notable exception to the warmth has been the Pacific Northwest where snow, ice and rain have kept winter alive.

This time last year, officials were worried about a heavy winter snowpack and its potential to create massive flooding -- a scenario that played out in many areas.

NOAA

Now, however, the threat isn't snow and flooding but heat and drought.

"What a difference a year makes," Laura Furgione, deputy director of the National Weather Service, told reporters at the agency's annual Spring Outlook news conference.

The drought concerns focus on west Texas and New Mexico -- and more recently Georgia, three-quarters of which is in severe, extreme or exceptional drought.

Drought and dry weather also raise the chances of wildfires.

In the Chicago suburbs, warmer weather was tied to four brush fires in three counties. One destroyed a bar and killed six horses, the Morris Daily Herald reported.

"It does seem like these fires are popping up early," local fire chief Ron Hoehne told the Daily Herald. "I can only assume it's because of a lack of snow or rain so far this year."

So is global warming behind the temperature increase? While "extreme events like we've seen are consistent" with warming, O'Lenic said when asked at the news conference, "it's impossible to connect any single event like this one with climate change." 

D.C. Cherry Blossom Festival blooms early

He also cited two naturally occuring factors: La Nina and what's known as the Arctic Oscillation, a measure of changing atmospheric pressure.

The Arctic Oscillation flipped from last year, when it helped create conditions for heavy snow, O'Lenic noted, so this winter has seen "the other side of the AO coin," with cold Arctic air being blocked from coming down into the U.S.

Last winter also saw a strong La Nina, a cooling of the Pacific Ocean, that lasted through spring and impacted weather globally. La Nina did return this winter, he added, but this time it "is fading fairly rapidly."

Reuters and The Associated Press contributed to this report.

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