IEM Daily Feature
Thursday, 01 September 2022

Is it fall?

Posted: 01 Sep 2022 05:30 AM

The date that ends the summer season is always debatable. Some say 31 August, others say Labor Day Monday, and others say 21 September. Is there a way to quantify this? Well, if you consider the hottest 91 day and coldest 91 day stretch of days over a given period of time, what drops out in between those two periods can be assigned spring and fall. The featured chart does just that with the top panel showing the trailing 91 day average temperature for Ames, the middle panel showing the date of maximum trailing value each year on record, and the bottom panel showing the number of days between this start date and the start date of the coldest 91 days (the length of fall season). So the 2022 value appears to have presently peaked for Ames back on 29 August, but the near term forecast has temperatures that may allow this value to peak again over the coming days as early June was rather chilly (warmer days in Sept replacing colder days in June for the 91 day average). That ambiguity aside, the bottom panel is sort of bad news for fall season lovers as it indicates the average length is only 86 days, so less than an equally split season around 91 days.

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Tags:   fall