Glenn Zimmerman’s long-range summer 2020 forecast

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ST. LOUIS, Mo. – What does the summer forecast look like? The FOX 2 weather team brings you the summer forecast.

Flood outlook:

Last summer, how many days did we hit triple-digit heat? The answer is zero. We hit 97 degrees three times, twice in July and once in August. But we never hit 100 or higher which is something odd. Part of the reason for that is that we had the 15th wettest summer on record and with that, major flooding. While we are still running above normal for rainfall this year, the flood outlook is for lower rivers this summer.


June is one of the wet months of the year. I don’t think that is different this year. The good news is that farmers have been able to get crops in the fields, so June rain is a good thing. June can be a severe weather month, but we see very few tornadic storms regionally in past Junes. Look for a few strong storms, with a higher than normal rainfall. Temperatures are a tricky story. May has been cool thus far, but I suspect that a solid push of warm air is ready to flip that switch. I think we will quickly turn to summer temps in early June and stay there all month.


July 14th 1954 is a date for the ages in St. Louis. It hit 115 degrees and stands as the hottest day in St. Louis history. Since then, we’ve had some hot Julys. The summer of 2012 is one you may remember. This July’s temps should be governed by one major factor: the sea surface temperatures in the Atlantic and in the Gulf. In both cases, they are above normal, and will affect the air here in the region. Specifically, low temperatures will rise above normal. When morning lows are warm, afternoon highs get a jump start on the warmup. So highs should stay above normal too. Warmer lows also mean more moisture in the atmosphere, so humidity will be higher and that will lead to heat-based, afternoon type storms. Quick downpours and isolated severe storms are the rule. Historically, the tornado threat in July is pretty low.


August means back to school! We will wait to see how schools will operate this Fall, but back to school always means some very hot days. August record highs are all over 100 degrees, while average highs drop from the upper 80s to mid-80s through the month. Nothing really points to a major shift in the normal. But, like July, morning temps stay warmer than normal and that will affect the daytime temps. So, a warmer than normal August. We may see a day or two near 100 this year. Rainfall is also based on the warm and humid lows with higher humidity, a higher risk of above-normal rainfall this August.

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