The Washington Post

When is it cool enough to shut off air conditioning?

Prior to yesterday, Washington, D.C. had six straight days of highs of 90 or higher. The temperature averaged ten degrees above normal during that span. Now, for at least a few days, the pattern has reversed, and temperatures are at or below average. In fact, Monday was the first below average day in the last 25. Of particular significance, the low the last two nights even at the urbanized Reagan National airport dipped to 65 and 64 (and to 61 and 53 at the more rural Dulles).

The sudden shift in temperatures no doubt inspired many to open up their windows and shutoff the energy hogging air conditioning. But as comfortable temperatures are a matter of individual preference, I thought it would be interesting to pose the poll question, how cool is cool enough to allow mother nature to act as our cooling machine?

Of course, another way of asking this question might be to ask when day time highs are cool enough to turn it off, or, as our friends at WJLA polled readers, how hot does it have to be to turn on the A/C? And, if you wanted to get technical, you would add dewpoint or humidity into the equation...

(Note: Think the switch in temperature regime is dramatic here? Consider Chicago, which went from having its hottest early season [June] period in 78 years, to having its coolest June 9-13 period in five years. Some there might be turning on the heat! More at the ChicagoWeatherCenter...)

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.


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