This weather pattern is as volatile and extreme as it can get across North America. All-time temperature records are falling like dominoes in parts of California, with at least three stations tying or surpassing their previous maximum temperatures ever recorded.
The National Weather Service office in Los Angeles proclaimed that the temperature reading at Pierce College was 121°F/49.4°C – the warmest day in L.A. County history. These temperatures create critical fire weather conditions; consequently, forest fires continue to ravage uncontrolled across the state.
The 121° high temperature at Woodland Hills official site (Pierce College) was also the highest official temperature ever recorded in L.A. County as well as Ventura, Santa Barbara and San Luis Obispo Counties. Click the URL for more details #cawx #LAheat https://t.co/wDCq45s0No pic.twitter.com/TAZuWF2vtG— NWS Los Angeles (@NWSLosAngeles) September 6, 2020
There wasn't much relief near the beaches. It very well might have been the warmest temperature in the Americas within this kind of proximity to an ocean. San Luis Obispo, a small city 300 km north of Los Angeles, soared to nearly 49°C, just a 10-minute drive from the Pacific Ocean.
Incredible heatwave across coastal California, w/multiple locations setting new all-time records (& many spots breaking monthly/daily records). @extremetemps thinks San Luis Obispo's 120F reading may be hottest on record for so close to an ocean *anywhere in the Americas! #CAwx pic.twitter.com/8o58I6d0Er— Daniel Swain (@Weather_West) September 6, 2020
Neighbouring states to the east have been sweltering, as well, including Colorado. Denver recently set a new benchmark for September warmth but is now bracing for one of the more extreme temperature swings in the city's history.
Scorching temperatures peaked well into the mid-30s. As thick wildfire smoke drifted across the region, the National Weather Service issued a rare early September winter storm watch. Up to 30 cm is forecast for the higher terrain in the Front Range, the mountain range west of Denver.
THE DAY AFTER TOMORROW?
How about this hourly forecast in Cheyenne, Wyoming... 🥵——>❄️ pic.twitter.com/w0EYkMyTam— Tyler Hamilton (@50ShadesofVan) September 6, 2020
A unique feature of this weather pattern change is the speed at which the temperatures plummet. It's conceivable you could be in southern Wyoming sweltering outside Monday afternoon (with temperatures in the lower 30s), and by Tuesday, dealing with an unwelcome snowfall.
On Saturday, Denver hit 38°C, the latest that warm on record. And, by Tuesday morning, with temperatures falling well below zero, it is likely going to be the earliest on record for recording a -4°C. It's highly unusual to squish these types of climate extremes so close to one another.
The cold air continues to plunge south across New Mexico, with Santa Fe set to record snowfall while warm temperatures cling on across southeastern portions of the state.