As temperatures generally head down across the nation this week, the Southwest will buck the trend and continue warming up.
The 90s and 100s that were felt in some areas this weekend will be commonplace early this week across many areas, most notably in California where the warmth will be nearly unprecedented for this time of the year.
In Fresno, it was the hottest start to October in 25 years.
Unusually strong high pressure centered over the Great Basin will reinforce the offshore flow that has been driving the southwestern warmth over the past several weeks.
Since the beginning of September, cities like San Diego, Los Angeles and Las Vegas have averaged several degrees above normal.
Through Tuesday, afternoon temperatures in those same locations could run as high as 15 degrees above normal. This will be more than enough to challenge some long-standing records.
In Sacramento and Fresno, record-high temperatures in the low 100s will be in jeopardy of falling early this week.
Even normally cooler San Francisco, which typically enjoys most days in the lower 70s this time of year, will take a run at the mid-80s again on Monday, which would rank it among the warmest days this year. Temperatures reached 87 degrees on June 16.
Typically hotter parts of Greater L.A., including Burbank and the Inland Empire, will reach triple digits. Even residents and visitors to the Pacific Coast will need to break out the shorts.
This unusual warmth has been well advertised here at AccuWeather.com.
AccuWeather.com Western Expert Ken Clark warned on his blog last week that excessive heat was on its way. Clark also warned about the potential effects of the heat on health.
"It is not advisable for anyone to overexert themselves from the middle morning hours into the early evening when it is the hottest," says Clark.
Both Clark and AccuWeather.com Meteorologist Anthony Sagliani added that very dry air would increase the fire threat.
"Relative humidity levels will plummet to less than 10 percent in many locations," said Sagliani. "With most of the region abnormally dry, a mere spark could ignite a fire; throw in gusty afternoon and evening winds, and an explosive fire threat will be present."
Though the record-challenging heat will be confined to early this week, the unseasonably warm air will persist through midweek before more-seasonable temperatures take hold this weekend.
A blast of chilly air from western Canada will focus toward the northern Plains and not the interior West during the middle of the week.
Conditions will improve across the Northeast on Friday as this week's nor'easter shifts away from the region.
A siege of Pacific storms will continue to drench and blast the coastal Northwest into next week and will be joined by Ana.
After many locations over the Plains feel like late summer this weekend, the record-challenging warmth will expand to the Northeast next week.
The disturbance responsible for drenching South Florida downpours will swing toward Bermuda this weekend, while the former Tropical Depression 9 lurks in the northwestern Caribbean Sea.
The NFL returns to London this weekend amid a mild stretch of weather.
Heat building across central South America this weekend will set the stage for adverse weather next week.
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