How unusual was this cold first half of May?

Tulips bloom around the Wisconsin state Capitol during eight straight chilly May mornings with overnight lows in the 30s.
(Credit: Ruthie Hauge, The Capital Times)

The first two days of this month had high temperatures of 87 and 84, respectively, and daily average temperatures (the average of the daily high and daily low) that were 15 and 19 degrees above normal.

In the next 12 days, the daily average temperature has been just shy of 6 degrees below normal. In fact, during that nearly two week stretch, nine days have had overnight lows in the 30s, including a streak of eight straight days from May 7 through Friday. The morning low on Tuesday was 30 degrees — notably cold and memorable for most of us, but only the 61st coldest morning in the first half of May in Madison’s history, far behind the all-time lowest of 19 degrees recorded on May 1, 1978.

However, the streak of cold mornings we have just endured is much more unusual. In fact, only four eight-day streaks of early May mornings with a low temperature at or below 39 degrees have occurred in Madison history — in 1971, 1976, 1989 and this month.

During this unusual spell of persistent cold nights, we have also been falling behind in precipitation. For the month of May, we are already 0.92 inches below normal and we are only halfway through the month. Coupled with our unusually dry April (and dry winter months of December-March) we are currently running 5.21 inches below normal in precipitation since December 1.

That is a substantial deficit which will require excessive late spring and summer rains to remedy. So, with the near-certain approach of warmer weather, attention to our accrued water deficit will become more urgent.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at or

Category: Meteorology, Seasons

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