Breaking down September’s heat: Not normal, but no records set yet

I’ve had several people send me messages and ask in person about the heat wave we just experienced last week.

The theme of shock that temperatures could be this hot in September was common. While it’s not normal for highs to reach into the 90s in September, it can certainly happen. So let’s break down the numbers.

So far this September

As I write this article (Sept. 15), we’ve had 11 days above normal. Typical highs this time of year should be around 80 degrees. Four days over the past two weeks reached into 90s.

Yes, these days were more than 10 degrees above normal, but they did not break any records. In fact, for the Dayton area, 90-plus degree days have been recorded in history all the way through the end of the month. Now that would be unusual.

Hottest Septembers on record

No surprise here: When I looked at the average monthly temperature so far this month for the Dayton area, it proved to be above normal. These temperatures are an average of the daily highs and lows through a particular date in the month.

By September 15, the average temperature is 68.5 degrees. Currently, the average monthly temperature is 73.4 degrees. It’s too soon to say if this month will break any records, but it’s unlikely it will be the hottest September ever recorded. Data by the National Weather Service shows the hottest September on record was in the year 1900 with an average monthly temperature of 72.83 degrees. That year the month ended with 12 90-degree days.

Looking ahead

According to the NWS Climate Prediction Center, the rest of the month is projected to have a better chance of being above normal for temperatures compared to below. Southwest Ohio falls somewhere between a 50 to 60 percent chance to be hotter than normal. That being said, it’s not likely we would see high enough temperatures to be considered the hottest September. Of course, we will have to wait and see.

This heat may also come with near-normal precipitation. That’s not necessarily a good thing as September tends to be one of the drier months of the year. On average Dayton receives a little more than 3 inches of rain for the month. And so far this month, its only received 0.01” of rain.

Drought monitor

After a very wet start to spring, summer is ending on a very dry note. According to the U.S. Drought Monitor, although dry weather can be good for crop maturation and corn dry down, the wet spring delayed planting, so some crops may be behind schedule and could use rain for filling (mainly soybeans).

A good portion of Southwest Ohio ranges from abnormally dry to moderate drought. Clark, Greene, and Miami counties appear to be the hardest bit by these dry conditions.

The U.S. Drought Monitor is released every Thursday. It’s possible moderate drought conditions may be expanded to include more of our region due to the lack of rain and hot temperatures.

You can find updates on when to expect rain and when this dry spell will end on WHIO-TV and on

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