US — Unseasonal snow has fallen in parts of the northwestern United States, while a heatwave is forecast for the eastern United States. A strong cold front from the northern Pacific moved into the western U.S. over the weekend.

Temperatures from the Canadian border to California have been 5-10 degrees Celsius below the norm since Friday. Even further north, some areas experienced temperatures more than 10 degrees Celsius below normal. This cold front delivered the first substantial rainfall in weeks to several parts of the northwestern U.S. Snowfall occurred on Sunday at elevations as low as 1,800 meters in Idaho, Montana, and Wyoming, where the typical summer snow line is approximately 3,300 meters.

The cold front's lightning strikes posed an ignition risk to dry vegetation across the western U.S. Heightened winds also contributed to the spread of existing fires in the region. The gustiest conditions over the weekend were observed in Utah, Colorado, and Arizona, where several major fires were already burning. Strong winds are expected to shift north into Wyoming on Monday.

Wildfire damage occurred on the banks of the Colorado River in Mack, western Colorado. The Cottonwood fire also burned near Beaver, Utah, on Saturday.

Forecast models indicate that high temperatures could reach 40 degrees Celsius (104 degrees Fahrenheit) in New York, Philadelphia, and Washington D.C. on Thursday and Friday. Night-time lows in these cities are projected to remain above the high 20s Celsius. The average daily high in July is 29 degrees Celsius in New York and 32 degrees Celsius in Washington D.C. The temperature record for New York is 42 degrees Celsius, while Philadelphia and Washington D.C. both have a record of 41 degrees Celsius.

Why It Matters

The simultaneous occurrence of unseasonal snow in the western U.S. and a heatwave forecast for the eastern U.S. marks contrasting weather patterns across the country. The below-normal temperatures and early snowfall in the West, coupled with strong winds, created conditions that impacted wildfire activity. Conversely, the anticipated high temperatures and warm overnight lows in major East Coast cities could pose health and infrastructure challenges.