How Bad Has Chicago’s Spring Weather Been?
We get questions!
Actually, sometimes people ask questions and I take the liberty of answering them. But I thought it would be an interesting question to answer, since it involves trying to quantify a subjective experience: what is "bad" weather? I took the April data for the past five years—because I figure April is the first month that we, as Chicagoans, can fairly expect something like consistent spring weather, and five seemed like a reasonable assumption for what a person can "remember"—and looked at the numbers.
* Temperature: The average monthly temperature in April, as of 2011, was 47.7 degrees. The departure from normal was -0.1 degree. Which doesn't sound bad, and wasn't as bad as prior Aprils. But that doesn't tell the whole story. The average high was 56.3, the lowest average high in five years. The average low was 39.3, only the third lowest average, but generally speaking, people are going to be experiencing the highs more than the lows, since that's when they're outside, or at least wanting to get outside. Verdict: Worst, sorta
* Wind: The average wind speed was 11.8 miles per hour... 0.1 mph higher than 2007. Verdict: Worst, barely
* Precipitation: 4.90 inches total, 0.6 of snow/ice/hail. 16 days with more than 0.1 inch. 2009 had more precipitation (5.19 inches, 2.1 of snow/ice/hail)... but ties with 16 days of 0.1 inches or more. I'm going to give it to 2009, but it's close. Verdict: Not the worst, barely
* Sun: 1 clear day in April 2011 (!); 11 partly cloudy; 18 cloudy. Compare to 3/18/9, 5/12/13, 4/15/11, 6/13/11. That one wasn't even fair. Verdict: Worst
* General crappiness: The NOAA recognizes certain atmospheric conditions like fog, heavy fog, thunder, ice pellets, hail, freezing rain, duststorm, smoke or haze, blowing snow, and tornadoes. I lumped them all in to bad weather, and gave each day a point for each category, and then counted the days with some form of crappy, depressing weather conditions. April 2011 had 32 general crappiness points over 21 crappy days, compared to 23/13, 23/15, 22/15, 24/14. Verdict: Worst
* Barometric pressure: Low pressure is associated with storms, physical ill being (in theory). The lowest pressure for an April in the past five years? 29.17 inches in April 2011. The average barometric pressure was also the lowest (29.86; all other years were above 29.90). Verdict: Worst
Conclusion: April 2011 is clearly the worst April in five years. If you were thinking this weekend that this has been the worst spring you can remember, I think you can fairly say that, up until that point, you are right. If you were thinking it's the worst more because of conditions instead of temperature, you're both right and particularly observant.
So there we have it: 2011 is officially the worst spring you can remember.*
Photograph: Whet Moser