When will Chicago see its first 70-degree day this spring?

Dear Tom,
When will Chicago see its first 70-degree day this spring?
JFY Pools, Marengo
Dear JFY,
Ahhhh, 70 degrees! Its first springtime occurrence is welcomed by many Chicagoans. Like many temperature features in our wide-ranging climate, though, the date of its first arrival has varied greatly through the years. In Chicago’s official temperature records dating from 1871, the earliest occurrence of a 70-degree high took place in the winter: On February 11 in 1999 the mercury shot up 70, but the warmup was short lived because the high the next day was only 32 degrees. Chicago’s most delayed onset of 70 degrees occurred back in 1874, a year in which persistently chilly temperatures lasted well into the spring season. The season’s first 70-degree reading that year was delayed until May 7, when it reached 70 (and was followed by five additional mild days).

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