Is Summer Over? Midwest Cities Rack Up More than Two Weeks of Below-Average Temperatures

Jonathan Belles
Published: August 12,2017
The midsection of the country has been in the midst of a summer break from heat in recent weeks, and if you're a fan of summer heat, it isn't looking good for a return to the dog days. At least not yet.
If you're from the central or northern Plains or Midwest, you're probably asking where summer went.
More than a dozen cities have had 14 or more days of below-average temperatures since July 15. Over three dozen cities have had more than 10 days of below-average temperatures since mid-July.

Selected communities with more than ten days of below average temperatures since July 15 are marked with blue and purple dots (15 days).
(NOAA Regional Climate Centers)

The last week in July and the first week in August have been below average across the central and northern Plains, with some communities being cooler than average for the entire first week of August.
(MORE: August 2017 Kicks Off With Temperature Extremes, Rare Tornado and Flash Flooding in Major Metros)
For instance, Lincoln, Nebraska, has seen 15 days below average since the middle of July, including the first eight days of August. Typically, the star city sees highs in the upper 80s and lows in the mid 60s for the first week in August. This August, though, the city has seen several days with highs in the 70s and low 80s, with one day even failing to get out of the 60s.
Little Rock, Arkansas, has racked up 17 days of below average temperatures since the middle of July, a time where temperatures are typically at their peak for the year.
So far, though, temperatures are roughly five degrees below average due to occasional early season cold fronts. Temperatures in the 90s are usually a sure thing in the first part of August, but Little Rock has gone 1 for 10 for highs in the 90s so far this month. Temperatures even failed to get into the 80s for one day on August 7th.
States that have spent the first eight days of August below average include Arkansas, Colorado, Kansas, Louisiana, Minnesota, Missouri, Nebraska, Oklahoma and South Dakota.
(MORE: First Snowfall of the Season for the United States is Coming)

Departures from average, in degrees, over the last two weeks.
(Southeast Regional Climate Center)

How can you have 2-3 weeks of below average temperatures in the heart of summer?
There has been zonal, or mainly west-to-east, flow across the northern United States with just occasional dips in the jet stream. This pattern doesn't allow for big pattern changes that would rush in a new temperature regime.
As August began, the jet stream dug into parts of the Midwest a bit more, allowing temperatures to be as much as 15 degrees below average for a day or two.
The occasional dips in the jet stream have been enough to keep it from being scorching hot, but not enough to make it actually cold. That said, there have been a few days this August of much below temperatures, but slightly-above-average temperatures in July, as the pattern settled in, have equaled those out.

Will Summer Return? 

At least for the next week, cooler than average temperatures are in store for the Plains states, but the temperature pendulum may begin to swing in the other direction toward the end of the month.
As with all stagnant weather patterns, it will likely take a large-scale weather system to make the jet stream more amplified, which is hard to come by in the summer months.

Setup for cooler conditions to persist in the midsection of the country.

(MAPS: 10- Day Forecast U.S. Highs/Lows)
Long-range model forecast guidance is showing signs that warmer temperatures may finally appear in parts of the Midwest by mid-late August.
A trough, or dip in the jet stream, will become more anchored in the Pacific Northwest toward the end of the third week of August, bringing with it a slow shift to warmer conditions in the center part of the country as a ridge, or bulge in the jet stream, builds downstream across the midsection of the country.

Temperature outlook for August 17-21, 2017.
(Climate Prediction Center)

(MORE: Pacific Heat Wave is Finally Coming to an End)
Stay tuned for updates on this possible pattern swap.

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