Hottest summer on record in Phoenix

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By Mike Gertzman By Mike Gertzman
By Mike Gertzman By Mike Gertzman
By Mike Gertzman By Mike Gertzman

PHOENIX -- If this summer felt hotter than previous summers in the Valley that's because it was.

This was the hottest summer on record in Phoenix, according to the National Weather Service.

The record takes into account both the afternoon highs and overnight lows.

Technically, fall starts on Sunday with the Autumnal Equinox at 1:44 p.m. That's on the astronomical schedule.  For climatological summer (June, July, August) we just wrapped up our hottest summer on record for Phoenix.

The average high was 106.4 degrees (5th highest summer average high) and the average low was 83.7 degrees (highest of all time for average summer low). 

That brings the overall summer average temperature to 95.1 degrees -- the highest ever recorded for a summer average in Phoenix.

That beats the previous average summer record high - 94.9 degrees in 2007. This year and the past two years account for three of the top 10 years.

What's to blame? There were many new records set for overnight lows caused by urbanization -- the urban heat island effect. The atmosphere has a harder time radiating heat and cooling off as the desert is covered up with roads and buildings.

We've had 108 days at 100 degrees or more, with more still to come this year.

There have been 25 days at 110 degrees or more, with the hottest day of the summer at 119 degrees on June 29.

The Associated Press contributed to this report