Heat map

A northern bulge in the jet stream is causing consistently high temperatures in the American Southwest.

CASA GRANDE — As record temperatures continue to occur around the American Southwest, the culprit is actually something that isn’t there.

According to Alex Sosnowski, a senior meteorologist at AccuWeather, the scorching heat is the result of a lack of moisture coming from monsoon storms. Arizona continues to be far below the average precipitation levels for this time of year, as the monsoon season started late and so far has not brought a lot of rain.

As a result, temperatures that have been challenging records over the past few days are expected to continue this weekend and even increase going into next week. Temperatures in Pinal County and the Phoenix area are expected to cool off slightly on Sunday and early next week, but then swell to the 110s by Wednesday.

The consistently high temperatures, Sosnowski said, are caused by a northward bulge in the jet stream, combined with high pressure at the surface.

“When the jet stream bulges northward over a particular region, the air aloft is warm and it is easier for temperatures to soar near the ground as opposed to when the air aloft is chilly,” Sosnowski said.

When the jet stream flattens, as it is expected to do shortly beginning Sunday, the temperature could then return to the seasonal averages, which is typically in the upper 90s or lower 100s. This puts the record heat experienced lately at about 10 degrees above normal.

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