Does not compute! That must be what residents of Iowa and the Midwest have have been saying to themselves on Tuesday as a ferocious heat wave unprecedented in intensity for so early in the year sent temperatures soaring as high as 108°. Just two weeks ago, the deepest snowfall ever measured during any May of record buried a wide swath from Arkansas to Minnesota, with Iowa breaking its all-time snowfall record for May (13” accumulation at Osage on May 1 - 3.) And how's this for a definition of "Weather Whiplash": Sioux City, Iowa had their first-ever snowfall on record in the month of May on May 1 (1.4"), but hit an astonishing 106° yesterday. Not only was this their hottest temperature ever measured in the month of May, but only two June days in recorded history have been hotter (June, 10, 1933: 107° and June 21, 1988: 108°.) On May 12th they registered 29°, and thus had a 77° rise over 56 hours (from 6 a.m. May 12 to 1:30 p.m May 14.)The hottest temperature of all on Tuesday was 108° at Tekamah, Nebraska. This is just 2° short of warmest temperature ever recorded in the state of Nebraska during May: 110° at Broken Bow in 1895 (exact day unknown.) Numerous all-time early season heat records were set on Tuesday, making the event the most notable May wave in the Midwest since a multi-day event in 1934. That heat wave was not preceded by unusually cold weather, which is what makes the May 2013 Midwest heat event truly extraordinary. A few notable cases of "Weather Whiplash" from the May 14, 2013 heat wave:
- Chicago, Illinois hit 91°, after hitting a low of 36° the previous morning. The 1-day temperature swing of 52° was the city's greatest on record for the month of May.
- Rochester, Minnesota, where 14.5” of snow fell just 10 - 12 days ago (4th greatest snowstorm for any month on record), saw an all-time early season heat record of 97° on May 14th. The previous day, May 13th, it was 32° in Rochester--a 65° rise in temperature over the course of 36 hours.
- Omaha, Nebraska hit 101°, the earliest 100° on record (old record 102° on May 29, 1934). It was 32° in Omaha on May 12th! That tied for the coldest so late in the season with 32° on 5/13/1997 and also on 5/15/1983.
- Albert Lea and St. James, Minnesota hit 102° (hottest in the state on Tuesday.) Both cities had May snow less than two weeks previously. Tuesday morning, it was 27° at Crane Lake and Silver Bay, for a same-day state temperature spread of 75° in Minnesota. This is a relatively common figure for California or Texas, but almost unprecedented for a Midwestern state.
- Minneapolis hit 98°, the hottest so early in season (next is 99° on May 22, 1925). May record is 106° on May 31, 1934 (the only time 100° has been measured during May).
- Norfolk, Nebraska hit 103°, the hottest temperature ever measured so early in the year (previous record: 103° on May 25, 1967. A daily record low of 29° was recorded on May 12th, just two days previous.