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.
As July draws to a close, a storm system swinging up from the Deep South will bring downpours that will break the back of the heat wave in much of the northeastern United States.
Heavy downpours will raise the concern for flash flooding along the Gulf Coast and lower Mississippi Valley through midweek.
A stifling heat wave will remain entrenched across the Northeast much of this week, despite a brief reprieve in humidity for some.
Dangerous heat will surge northward and send temperatures rising across the northwestern United States this week.
Severe thunderstorms rumbled through the Northeast on Monday, lashing the region with damaging winds while also unleashing heavy downpours that triggered flash flooding.
Here are five easy ways to stay cool in sweltering summer heat.
Pollack, MD (2008)
Softball-sized hail shattered cars and windows.
Bridgetown, NJ (1803)
Tornado at 8:00 a.m. "The storm increased, and for the space of about three-quarters of an hour the lightnings were incessant and the thundering most awfully majestic." "The body of a covered wagon, taken from the wagon house, torn from from the springs, shattered and set up on end, the axel trees broken and 3 of the wheels torn from the same were found in different places at a distance of 50 feet." "One new wheel of a new heavy strong wagon broken entirely to pieces."
Hurricane near Jacksonville; $2.5 million damage in East Florida.