A strong cold front swept into the western US over the weekend and turned parts of the Rocky mountains white in midsummer, with snow falling as low as 1,800 metres on Sunday in Idaho, Montana and Wyoming. The same system was still pushing cold air and more snow into the region on Monday, with several inches expected to pile up at higher altitudes.
That is the story readers are searching for now: a sharp break from summer warmth that arrived suddenly and spread widely. Since Friday, temperatures from the Canadian border to California have been running 5-10C below normal, and the cold pattern is set to linger at least through Monday before it begins to ease.
The low-elevation snow is unusual even by mountain standards. In the higher terrain, forecasters expect accumulation to build into several inches, while the strong winds linked to the front are due to move north into Wyoming on Monday. In a stretch of the country already dealing with drought in many places, the system brought the first significant rainfall in weeks to parts of the north-west US and also heightened the danger posed by wildfires as wind and lightning moved through the dry landscape.
The contrast with the east is striking. Forecast models suggest highs could possibly reach 40C on Thursday and Friday in New York, Philadelphia and Washington DC, with night-time lows struggling to fall below the high 20s celsius. July averages are far lower, at 29C in New York and 32C in Washington, and the all-time records of 42C in New York and 41C in Philadelphia and Washington show how much heat the cities would have to absorb if that forecast verifies.
For the West, the immediate question is not whether the air turns milder, but how much snow and wind arrive before it does. The cold front has already delivered a rare summer snowfall in Idaho, Montana and Wyoming, and Monday should finish the job in the mountains before the pattern shifts.
