Elwell: Soaking rains keeping summer heat in check, for now

Heavy rainstorms like this one that set a daily rainfall record on June 23 keep temperatures down in the region. CHUCK HAMLIN / STAFF

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Heavy rainstorms like this one that set a daily rainfall record on June 23 keep temperatures down in the region. CHUCK HAMLIN / STAFF

If you read my article last week, you likely recall me mentioning how we are heading into the hottest part of the year.

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July, on average, has the warmest temperatures overall of any month here in the Miami Valley. Now that doesn’t mean we can’t get hot in August and September, but as far as persistent heat, typically we see that in July through early August.

As we approach the third week of summer, temperatures have struggled to even stay near normal. We just enjoyed a weekend where temperatures were around 5 degrees below average and the humidity remained low. It was honestly about as nice as you can expect. Looking back at June, most of the days were near or below average. However, a mid-month heatwave did push the numbers so that June ended as being a normal month.

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But since late June, a series of heavy rain producing storm systems have helped keep temperatures in check. Just in the last two weeks, most of the Miami Valley has had over 3 inches of rain with some areas picking up over 5 inches. With ground moisture now being plentiful, expect that temperatures will likely stay shy of the 90-degree mark. Research across the Miami Valley has shown it is difficult for high temperatures to exceed 90 degrees when rainfall amounts are running above normal. Now there are some exceptions, but not many.

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The reason is due to the simple laws of the water cycle and how the cycle also impacts the temperature. Obviously, on rainy days, the temperature is cooler, but the days following a soaking rain can be a bit cooler due to the added ground moisture. When there is moisture in the ground that is readily available for evaporation, that evaporation creates a cooling effect. It is much like when you get out of a swimming pool or a shower, the cooling effect you feel as the water begins to evaporate. It works the same way in the environment. If we can continue to have soaking rains at least once per week, then expect temperatures will not get too extremely hot.

However, keep an eye on the forecast over the coming two weeks. While this week we will have plenty of rain in the forecast, there are signs the pattern may begin to change allowing for drier conditions to develop. If this occurs and ground moisture begins to decrease, expect temperatures to increase.

You may be able to recall the summer of 2012 when we saw severe drought conditions develop, not only in Ohio, but across most of the central United States. In fact, some part of every state, including Alaska and Hawaii, was experiencing some drought conditions by the end of the summer in 2012. You may also be able to recall the number of afternoons spent near or above 100 degrees here in the Miami Valley that summer.

While I certainly don’t expect a repeat of 2012 later this summer, almost all indications are temperatures will climb back above normal later this month. The long-range outlooks released from the Climate Prediction Center show above average temperatures likely the rest of the summer and perhaps lasting well into autumn.

Eric Elwell is WHIO StormCenter 7 Chief Meteorologist. Contact him at eric.elwell@coxinc.com or follow him on Facebook and Twitter.

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