Melba Lara: You're listening to WBEZ. It was a dark and stormy night. That's the classic start to a scary story. But how many of our Halloween have been actually stormy? We got to wondering about Halloween weather history here in Chicago, and which nights have been the chilliest, the wettest, the foggiest and the spookiest. Illinois State Climatologist Trent Ford was kind enough to crunch the numbers for us, and he joins us now. Trent, Happy Halloween. 

Trent Ford: Hey, happy Halloween Melba. 

Melba Lara: You know, when I was a kid, I feel like all the Halloweens were kind of rainy and gray and cold. What's our typical trick or treating weather here in Chicago? 

Trent Ford: Yeah. So you know, from a temperature standpoint, actually, the Halloween temperatures are pretty mild on average. And these numbers go all the way back to 1872, for the City of Chicago, so a long, long time. Average high temperature, about 56 degrees, and average nighttime low temperature about 40 degrees. So oftentimes, when folks go out for trick or treating and that sort of thing, it's usually in about the 40 degree temperature range. 

Melba Lara: And what's the coldest Halloween has ever been? 

Trent Ford: Yeah, interestingly enough, so one of the earliest years of weather recording for Chicago: 1873, that was the coldest as far as the high and low temperature. A 31 degree high temperature during the day in 1873, and 23 degree low temperature that night in 1873. However, with that being said, much more recently: 2019, if you remember we had some snow, but also it was a very cold Halloween. The high temperature during the day was 33 degrees. So not a very warm Halloween just a few just a few years ago. 

Melba Lara: Yeah, not at all. Can you tell us what was the hottest Halloween that we had? 

Trent Ford: Yeah, hottest Halloween: 84 degrees in 1950. And it had a 63 degree low that night as well. So even the low temperature in 1950 was actually higher than our average high temperature on Halloween. So definitely a warm one there. 

Melba Lara: Yeah, we would take that anytime. And talk to us about rain, how often doesn't rain on Halloween? You know these costumes are not waterproof, necessarily. 

Trent Ford: That's right. Yeah, we think about the cold and protecting ourselves from the air in our costumes. But yeah, the rain is really the menace. So 36% of the Halloweens since 1872 in Chicago have had measurable rain, so it's a 100th of an inch or more. And of course as we know when it rains on Halloween, it's like everybody's worst nightmare, 40 degree rain, you know, real cold rain, but the wettest Halloween in Chicago overall was 2.26 inches for the day in 1994. So extremely wet Halloween there. 

Melba Lara: And Trent, I understand you've done some very objective and scientific research into which Halloween had the creepiest weather. Tell us what you found there. 

Trent Ford: That's right. Yeah, this was the fun part here, is thinking about the creepiest Halloween in Chicago and I think that my professional opinion lands us on 1984. So what I did is I looked at visibility, which has been measured hourly at O'Hare since 1946. So basically, if you look out how far can you see out and that gives us an idea about fogginess. And then also the National Weather Service and the folks at O'Hare report the kind of present weather conditions. Was it thundering, was it raining, was it snowing, and fog. So what we found is that the average visibility in 1984 between 6 and 10pm, just when all the mischief is happening, was a little bit less than two miles in 1984 which is actually pretty, pretty thick fog. And there was actually thick fog reported right around 7 or 8pm at O'Hare around that time. 

Melba Lara: All right, there you have it. Thanks for our spooky, scary weather history Trent, we appreciate talking to you. 

Trent Ford: Hey, it's always great being on. 

Melba Lara: That's our Illinois State Climatologist Dr. Trent Ford talking to us about weather history on Halloween. If you've got a question that you want answered in our weekly climate segment, you can email us at climate@wbez.org. This is WBEZ.

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