Western states experience unseasonally low temperatures but New York and Washington DC could reach 40C by end of week

Unseasonal snow has fallen in some parts of the US, while other parts of the country brace for a heatwave this week.

A strong cold front spread into the western US from the northern Pacific over the weekend, bringing an abrupt change in conditions to a region that had been experiencing high summer temperatures amid drought. Temperatures from the Canadian border to California have widely been 5-10C below the norm since Friday, and more than 10C below in some parts farther north. The pattern is expected to remain for much of the coming week.