Record-challenging heat to bake West during first full week of fall

After what has already been a hot and dry summer in much of the West, Mother Nature is set to turn up the thermostat again, despite the fact that the calendar says it is now fall. Residents will think it is the end of July and beginning of August and not the end of September and beginning of October.

"A prolonged wave of intense and, in some cases, record-challenging heat is on the way for the West as September comes to a close and October begins," said AccuWeather Meteorologist Renee Duff.

Following welcome rain late last week in the Pacific Northwest, the upcoming patten will be quite a change.

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"The warmup is likely to be most noticeable across the Pacific Northwest, where cloudy, rainy conditions kept high temperatures near to slightly below average from Wednesday through Saturday, in the 60s and 70s," Duff said.

The extreme heat will become established this week as a large dome of high pressure builds overhead.

While the magnitude of the heat will not rival what was endured earlier in the month, records could still be in jeopardy in some locations. However, expected highs are likely to be just short of establishing new records. That said, many cities will experience highs of 10-20 degrees above normal.

Even though there is only a small chance of daily records, other records could be set.

For example, Las Vegas notched its 96th day with a high temperature at or above 100 degrees on Thursday. This is the second most 100-degree days in a single year. The record is 100 days in 1947. The expected coming heat could make that record attainable.

Phoenix experienced its 129th day of 100-degree heat on Saturday, tying 2003 for second-most triple-digit days in a single year. The all-time record is 143 days in 1989. This city has already had 53 days at or above 110 this year, smashing the previous record of 33 days in 2011. Temperatures are not forecast to reach 110 during this upcoming heat.

Farther north, the heat will not be as extreme, but it will be quite a change from the cool air and rain of the past few days.

"By the middle of the week, Seattle is expected to approach 80 degrees Fahrenheit, and Portland, Oregon, could climb into the lower to middle 80s," Duff added.

In areas where rain has fallen this past week, such as in part of the Northwest, the fire danger has been lowered.

"Since the Pacific Northwest has gotten a thorough soaking, the risk of new wildfires being sparked amid the warmth will be low," Duff said.

Unfortunately, rain was still absent this past week, and has been for months, in some locations. In those areas, the fire danger will continue to be extremely high.

"However, farther south where 90s and triple-digit heat will reign and no rain has fallen in months, the upcoming heat wave will only worsen the ongoing drought and wildfire situation," Duff said.

Even prior to the heat fully ramping up, the fire danger will be heightened across portions of California due to dry, gusty winds into early week.

The bottom line is that even though it has gone from summer to fall and the calendar is about the flip from September to October, summer heat is not yet over in the West.

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