Sunday, August 2, 2015

West Coast Heat Wave Clinches a Record Hot July in Seattle; Heat Relief Ahead for Northwest and Northeast

Chris Dolce
Published: August 2,2015

Summer heat is gripping opposite sides of the country this weekend, including parts of the Northwest and the Northeast.
The heat has helped to clinch one of the hottest Julys on record for some Northwest cities. It's also helped set a record for the most 90-degree days in a year in Seattle and has given Portland its hottest temperatures since 2009. After a hot weekend, some relief will finally arrive early in the new week.
A substantial warm up also occurred for places that saw snow early last week in Montana, Idaho and Wyoming.
The Northeast heat will not be as extreme, but it will stick around into early week for some cities.
Let's break down the forecast details on this summery weather pattern for both regions.

Northwest: Clinching a Record Hot July


Current Northwest Temperatures














A strong ridge of high pressure built over the Northwest as the jet stream bulged northward to the Canadian border. This allowed temperatures 5 to 20 degrees above average to take hold across parts of Oregon, Washington, Idaho and Montana this weekend.
(MORE: Strange July Weather Pattern Brings Snow, Tornadoes)
The heat wave helped clinch the hottest July on record for the following cities (all data is preliminary):
  • Seattle: July 2015 average monthly temperature is 71.2 degrees. This beats the old July record of 69.5 degrees set in 2009.  This also beats out August 1967 (71.1 degrees) for the hottest of any month on record. Records date back to 1894.
  • Salem, Oregon: July 2015 average monthly temperature is 73.1 degrees. This beats the old record of 72.5 degrees for hottest of any month set in both July and August 2014. Records date back to 1893.
  • Eugene, Oregon: July 2015 average monthly temperature is 71.5 degrees. This beats the old July record of 71 degrees set in 1958. Records date back to 1912.
Portland, Oregon, saw consecutive days with 100-degree heat, topping out at 103 degrees on Thursday and 101 degrees on Friday. Thursday's 103 was the hottest temperature there since July 29, 2009. Those hot temperatures have vaulted Portland to its second hottest July on record with an average temperature of 73.9 degrees, falling just behind 1985 which had an average of 74.1 degrees.
Seattle saw its twelfth 90-degree day of 2015 on Saturday, which is a new record for the most 90-degree days in a calendar year. The old record was nine days set in 1958. The Emerald City averages just two days with 90-degree heat annually.
Eugene and Salem, Oregon, both set daily record highs on Thursday by topping out at 105 degrees. This was one degree shy of an all-time July record high in Eugene. Another daily record high of 103 degrees was set in Eugene on Friday. Eugene has also set a record for the most days in a year with temperatures at or above 100 degrees with seven days through Saturday, the previous record was five set in 1978. Daily record highs were recorded in both Eugene (100 degrees) and Salem (100 degrees) on Saturday.

Forecast Highs

Forecast Highs






























Farther south, Roseburg, Oregon, was one degree short of an all-time record high on Thursday when it topped out at 108 degrees. Friday's high was 107 degrees which set a new daily record.
For parts of central and eastern Washington, this round of hot temperatures probably won't be quite as intense as the late-June record-breaking heat wave. Spokane hit 105 degrees in late-June, but should hold near 100 degrees through the weekend.
In Northern California, Redding topped out at 114 degrees on Thursday, which set a new record for the date. Sacramento (downtown) set a daily record high of 107 degrees on Wednesday.
Boise, Idaho, squeaked just past 100 degrees on Sunday after recording a high in the low 100s Saturday. Idaho's capital should fall well short of its June 28 high of 110 degrees, which set an all-time record for June.
For parts of Montana, this is quite a change from the way the week started.  For example, Missoula, Montana, saw rain with temperatures in the upper 40s and 50s on Monday afternoon. Highs were in the low to middle 90s there on Thursday and Friday and temperatures reached 98 degrees on Saturday. Temperatures will climb into the middle to upper 90s through Monday.
High elevation areas that saw snow on Monday in the northern Rockies will also see significant temperature rises. Big Sky, Montana, reached the lower 80s on Sunday and Grand Targhee, Wyoming which saw 1.5 inches of snow early this week saw a high in the mid 80s Sunday.

Northwest Heat Relief Ahead


Cooler Temperatures Coming















Some heat relief will finally arrive early this week in the Northwest. The entire region will see temperatures trend back to early-August averages Monday-Wednesday as the upper-level ridge responsible for the hot weather shifts east.
Highs in the low to middle 80s are anticipated in Seattle during the first half of the new week. Portland will see temperatures in the middle 80s Monday and Tuesday, followed by low 80s Wednesday.
Upper 90s and low 100s will also be eliminated from parts of western Washington, western Oregon, Idaho and western Montana as the new week begins.

Northeast: Heat Wave Possible in Some Cities


Forecast Highs














This past Wednesday was the hottest day so far in 2015 in New York City (96 degrees) and Albany, New York (95 degrees). Concord, New Hampshire, set a daily record high of 96 degrees, beating the old record for July 29 of 95 degrees set in 1949.
Highs will stay a handful of degrees above average for mainly eastern sections of the region into early week.
For the most part, this heat in the Northeast will not be record breaking. However, the longevity of it is likely greater than we've seen so far this summer in some cities. Some locations could meet the definition for a heat wave in the Northeast, which is generally defined in that region as three or more days in a row with temperatures at or above 90 degrees.
(MORE: Daily Forecast Maps)
That said, there is a big difference between the way it felt Thursday and the way it will feel this weekend across the Northeast. This is because much drier air has filtered in behind a cold front that brought strong thunderstorms to the region on Thursday.
As a result, the humidity that has added to the discomfort dropped significantly, making the heat more bearable. For example, Washington, D.C. had an actual high of 92 degrees with a peak heat index of 103 degrees on Thursday. Friday's high was just as warm, but with lower humidity the heat index was not a factor.
New York City is likely to see highs mainly in the low 90s or upper 80s into Tuesday. So far this year, the Big Apple has experienced six days with 90-degree heat. Highs in the 90s were recorded on back-to-back days for just the second time this year on Tuesday and Wednesday.
Boston will see temperatures near 90 through Monday. On Saturday, Boston saw its fifth 90-degree day of the year.
Farther south, the Mid-Atlantic will sizzle through highs in the low to middle 90s through early week, including Washington, D.C. and Philadelphia.
Washington, D.C. has already seen its fair share of 90s in 2015, with 35 days total through Sunday. They will likely meet or exceed their annual average number of 90-degree days in the next few days which is 36.

MORE: Northern Rockies See July Snow

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