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David Epstein

Why does record heat keep hitting the West?

In Portland, Ore., on Wednesday, the high of 103 degrees shattered the 1986 record for the day, which was 96 degrees.
In Portland, Ore., on Wednesday, the high of 103 degrees shattered the 1986 record for the day, which was 96 degrees.Don Ryan/Associated Press

It sure has been a highly active summer around Greater Boston with rainfall and even some unusually cool air, but out West it’s been just the opposite: lots of heat and lots of dry weather.

Here’s the thing about this pattern, it’s all connected.

Next week a trough will prevent heat from reaching New England.

This week, triple-digit heat has been present across places which typically don’t see it very much. Portland, Ore., for example is going to get pretty close to their all-time high temperature, with Thursday afternoon forecast to reach near 104 degrees.

Other spots out west will also be approaching records. The map below has circles around those official observing stations most likely to break a record today.

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Last summer, the Boston area had lots of heat and little rain. This spring the pattern shifted, bringing an upper-level ridge to the western part of the country and plenty of heat out there. Remember Phoenix back in June and all of their days well into the 100-degree range? That pattern and the one this week are similar, just with the high-pressure system sitting farther north.

Changing climate and the heat

In Portland on Wednesday, the high of 103 degrees shattered the 1986 record for the day, which was 96 degrees.

Breaking a 31-year-old weather record isn’t an indication of climate change. However, what we continue to see are high-temperature records being broken not by a degree or two, but by five or even 10 degrees. When Burlington, Vt., hit 72 degrees in February, it broke the daily record by 17 degrees and the monthly record by 10.

Climate modeling suggests this pattern of breaking warm records by wide margins will increase in the coming years. So far this year, there have been 10 times the number of monthly warmth records as compared to low-temperature ones. This data fits the pattern we’ve seen for the past decade.

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While this hasn’t been a hot, dry summer in New England, it’s important to separate these weekly and monthly patterns from the bigger picture. New England summers have become warmer and wetter over the past 30 years. This doesn’t mean we can’t have a cool day, month, or even season within this overall change.

Weather is short-term, climate is long-term. In the shorter term, it appears the heat is going to remain out West through the middle of the month, with cooler air trying to spill into the Northeast from time to time. In other words, no big heat waves here.

Longer term, you can be confident New England will be breaking plenty of warm weather records in the coming years.


Follow Dave Epstein on Twitter @growingwisdom.