Chicago's earliest occurring 91-degree high temperature in 31 years followed by less than 36 hours frost and a 36-degree daybreak temperature early Monday morning.

Tuesday’s 91 occurred at O’Hare  at 3:22 p.m., close to the time that Midway Airport was logging a 90-degree high. Both readings were more than 20-degrees above the normal of 69. It was a weather turnaround of historic proportions.

Never before in Chicago had a set of May high temperatures increased by 55-degrees in less than 2 days time!

Jarring shift from wintry snows to mid-summer-level heat carries sections of the Plains and western Midwest  from a foot of snow to triple-digit temps in under 2 weeks               

Even more dramatic were the stunning weather changes which occurred to Chicago's west Tuesday. Soaring temperatures smashed records from Nebraska into western Iowa, Minnesota and western Wisconsin---areas which less than 2 weeks earlier had been crippled by a record-breaking foot or more of late-season snow.

Albert Lea, Minnesota recorded a 100-degree high Tuesday. Only 12 days earlier that city had been buried under a 10-inch accumulation of snow.

Iowa's state climatologist Harry Hillaker reported in a special weather statement out of the National Weather Service Forecast Office in Des Moines Tuesday that 100-degree or higher temperatures have occurred in the month of May on only 11 occasions since official weather records began in the state  in 1873. Even rarer have been 100-degree readings two weeks after a major snowstorm. Hillaker reports this has happened only a few times over that period.

Just 17 of the past 142 years have recorded 90-degree temps by May 14 in Chicago

For a 90-degree temperature to occur here by May 14 is a rare meteorological occurrence ---something which has occurred in only 17 of the past 142 years. That puts the climatological probability of a 90 this early in the season in Chicago at just 12%---far from a slam-dunk.

Abnormal heat breaks records across at least 8 states; sends earliest 100+-degree temps into a number of cities to Chicago’s west

For a second day Tuesday, temperatures records fell across a multi-state area as heat spread eastward out of the Rockies.

Omaha and Lincoln, Nebraska each recorded their earliest 100-degree or higher temperatures on record--- with highs of 101 and 100-degrees respectively. The same was true in Sioux City, Iowa where the mercury hit 106-degrees Tuesday---the hottest temperature ever recorded there in May. Sioux City’s  previous record May high had occurred 79 years earlier in the Dust Bowl year of 1934 when a 105-degree reading was logged.

In Rochester, Minnesota, Tuesday’s 97-degree high became that city's hottest reading ever recorded so early in the year.

Temps pull back 10-degrees Wednesday but remain well above normal; readings to peak in the low 80s

An unseasonably warm Wednesday is ahead despite a 10-degree pullback in high temperatures. The predicted high of 81-degrees will still be more than 10-degrees above normal.

Lake breezes Thursday and better organized easterly winds off Lake Michigan Friday are to lower temperatures further in the days ahead, especially in lakeside counties.

Predicted onset of warmer, more humid weather this weekend behind higher 7-day rainfall numbers

Warmth and increased humidity stage a comeback this weekend with temperatures returning to the 80s by Sunday and Monday, if current forecast trends continue. The influx of moisture will fuel t-storm clusters expected to occur in scattered fashion and separated by rain-free hours. Nonetheless, cumulative rainfall totals may well surge above normal in the coming week suggesting a wetter overall pattern may be coming together.

A more dramatic warm-up than the one predicted Tuesday has never occurred in Chicago during May. Tuesday's predicted temperature surge to a July-level high of 88-degrees at O'Hare would be a 52-degree increase from Monday morning's chilly, frost-generating 36-degree low. That would be a first here and establish a new record for the largest 2-day temperature surge in the month of May.

There have been past "day-to-next" temp increases of that magnitude at OTHER times of the year here. A 52-degree surge Tuesday would tie with eight other years since 1871 as the city’s 11th- largest increase over a two-day period.

It's been a decade since temps last warmed by that much over two days and that occurred April 13-14, 2003 when readings soared from  from 29 to 85-degrees.

Incoming warmth part of a warm surge which broke records across 9 Plains and western states Monday

The pool of abnormally warm air from which Tuesday's warmth emanates generated record-breaking highs across 9 states Monday---from California east to Montana, the Dakotas, Nebraska and Kansas.

Salt Lake City, Utah recorded its earliest 93-degree high on record.

Temperatures flirted with triple-digits in Kansas and  topped 100 out West Tuesday

Afternoon highs Tuesday neared triple digits in Kansas and topped the century mark in portions of Utah, Nevada, interior California and Arizona.

Highs of 99-degrees were recorded at Ulysses; 98 at Phillipsburg and 97 at Oberlin---all in Kansas.  Farther west, St. George, Utah hit 102-degrees while Fillmore---also in Utah---topped out at an even 100-degrees.

In nearby Nevada,  Laughlin reached 109-degrees and Overton hit 108 while Bullhead City, Arizona broiled at 108 and Parker recorded a 106-degree max.

Capped atmosphere means weak cold front to pass precipitation-free here Tuesday night despite influx of Gulf moisture and presence of strong wind shear

The prediction of surging dew points later Tuesday and Tuesday night, a sign of more humid air's arrival, plus forecasts of high atmospheric energy levels and a vigorous shift in wind speeds with height----what meteorologists refer to a vertical shear---would at first glance appear to support the eruption of powerful thunderstorms with a southbound cold front Tuesday night.  But computer models depict a "capped" atmosphere---one in which temperatures don't decline with height in their usual fashion, as well Chicago's position under the "nose" of a powerful pocket of upper level winds, as factors predicted to thwart what might otherwise be vigorous thunderstorm development Tuesday night.

This suggests the cold front will do little beyond producing a shift in Tuesday night's powerful ground-level winds here. Temperatures are predicted to hold at unseasonably mild levels 18-degrees above normal  overnight,

Influx of Gulf moisture with weekend warm surge could set the stage for several thunderstorms

It's late this week and over the coming weekend which pose the best chance of generating thunderstorms. They're likely to arrive in widely spaced clusters, suggesting many rain-free hours are likely to be interspersed with what looks to be a new round of 80-degree temperatures.

Quietest tornado/severe weather season in nearly 60 years could become more active here Sunday

Sunday afternoon or night could prove a different story.  Jet stream winds will be slicing through humid air in place by that time raising the specter of potentially vigorous thunderstorms in a severe weather season which, up to now, has been the quietest across the U.S. in nearly 60 years.