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Why is Arizona so hot this summer?

Unusual summer weather pattern
Posted at 4:13 PM, Aug 21, 2020
and last updated 2020-09-21 16:51:49-04

TUCSON, Ariz. — We are in the midst of what could become the hottest summer ever recorded in southern Arizona. This has many desert dwellers wondering why it is so hot! There are several factors, but the position of a strong ridge of high pressure is the main reason.

Usually, during the summer months, high pressure will establish itself to the east of Arizona and is in a good position to bring rain to southeastern Arizona. This year, high pressure has been wobbling back and forth over the top of Arizona.

This does a few things to our weather…

  1. It blocks sub-tropical moisture from being able to reach into southern Arizona. This also keeps our air drier.
  2. Drier air heats quicker and brings hotter temperatures. If high pressure is strong enough, high temperatures can easily run 5° to 15° above average. This has been common across southern Arizona this summer.
  3. Hotter days equal hotter nights. Adding to the overnight heat is our urban sprawl. As our cities continue to grow, it’s tougher to get temperatures to cool down at night.
  4. The lack of moisture also results in a lack of thunderstorms. Other than not getting the rain to help replenish our water supply, we also don’t get the rain to help cool our temperatures.

All of these things add up to a hot summer. Fortunately, in the next few days, we’ll get some help from Hurricane Genevieve. Genevieve is going to come close enough to Baja California to send some more moisture over the Sonoran Desert. We’ll see an upswing in thunderstorm activity through this weekend and slightly cooler temperatures.

Unfortunately, next week, high pressure will return to a position that will chase the thunderstorms away and bring back the heat. The good news is that we are approaching September when we have less daylight available. This will give the sun less opportunity for such strong daytime heating. However, extended forecast trends show above-average temperatures continuing and below-average rainfall expected as we finish summer and head into fall.

Looks like we’ll have to keep relying on air conditioning to keep us cool. Hang in there, winter is only four months away!