Hurricane Emilia strengthened into a major Category 4 storm overnight, but the system off Mexico's Pacific coast was no threat to land, forecasters said Tuesday.

Emilia's maximum gusts are 140 mph, but a "gradual weakening is expected to begin by tonight and continue through Thursday," the National Hurricane Center said in its morning advisory.

The storm was 680 miles southwest of Baja California and was moving west-northwest. No coastal watches are in effect.

The Pacific hurricane season has gotten off to a fast start. Emilia is the fifth named tropical storm, and four of the storms became hurricanes. Hurricane Carlotta made landfall on Mexico's coast on June 15 and took the lives of two children.

Hurricane Daniel, even farther off Mexico's Pacific coast than Emilia, weakened to a tropical storm overnight, with winds near 70 mph. It too was moving west and was expected to break up later in the week.

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