Record heat

PHOENIX (Arizona's Weather Authority) -- This weekend will mark the first time in more than six weeks that Phoenix is expected to see below-average high temperatures. Valley residents have waited a LONG time for a cool-down after a brutal summer of seemingly never-ending heat. As a meteorologist, I felt like a broken record talking about all of the records we were breaking!

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July 2020 was our hottest July on record, followed by an August that was also our hottest August on record. So, it won't shock you to know that this was our hottest summer on record for Arizona. Records kept at the National Weather Service in Phoenix go back to the 1890s.

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But the heat didn't end when summer officially came to a close at the end of August. We kept breaking records, adding to our triple-digit tally well into September and October. We're finally done with triple digits for the year, but check out where we ended up.

The most days Phoenix has ever seen of triple-digit heat in one year was in 1989 when we had 143 days. That was, until 2020, when we saw 145 days that hot.

When it comes to days of 110 degrees or higher, it wasn't such a slim margin. The previous record was 33 days in a year, and we saw 53 days that hot this year.

This next one will really blow you away. The previous record for the most days of 115 degrees or higher was seven days. We DOUBLED that this year with 14 days of intense heat of 115 degrees or higher. The hottest day this summer in Phoenix was 118 degrees on July 30.

A look back at the hottest days in Phoenix history

There are several reasons this summer was so brutally hot, including climate change and weather patterns. This past summer, high pressure was unusually strong and positioned in the wrong spot to help bring in monsoon moisture. With a ridge right over or just to the south of Arizona, we missed out on monsoon rainfall, cloud cover, and humidity that would have led to cooler temperatures. The weather pattern brought us the hottest summer on record for Phoenix also brought us the driest summer on record for Arizona. In Phoenix, we had only TWO DAYS of measurable rain all summer!

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The urban island heat effect is another reason for the hot conditions of summer 2020. The growth of our city means more buildings, homes, and asphalt, all of which absorb heat. The change to our local environment leads to slightly warmer afternoons and much warmer overnight lows. We're seeing more and more overnight lows in Phoenix in the 90s now during our summer months.

So, what's ahead for winter? The Climate Prediction Center says the La Nina conditions now present will continue through the winter. Typically that means above-average temperatures and below-average precipitation for Arizona. That's not always the case. Of the last 16 La Nina years in Phoenix, 10 winters have followed that pattern.

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Let's hope the storm moving in this weekend brings us some decent rain and a nice cool-down. I think we can agree we're all ready for that.


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