Chill spills into a second day after the coldest April open of the past 20 years Monday


March-level temperatures are back. The problem is, it’s April and temperatures ought to be warming—not reverting back to levels more typical of a month earlier. This development is just the latest in a string of unusual weather twists and turns which have characterized recent months here.


Chicagoans shiver through another day of 40s Tuesday but are casting a wishful eye toward the 60-degree readings predicted Thursday and the mid-60s which may occur here on Saturday.


Tuesday’s predicted 44-degree peak reading comes on the heels of Monday’s max of 41-degrees, a reading which made it the coldest April 1 here in 20 years.


At the Cell, Sox fans celebrated a 2 to 1 win over Kansas City in the team’s chilliest opening day weather at home of the past 33 years. Only four other Sox home openers have been colder: 1907 (38-degrees); 2003 (39); 1905 (40) and 1980 (40).


Early March-level temps Tuesday belie the fact that April is Chicago’s second-fastest warming month


April has historically been the city’s second-fastest warming month. Its normal temperatures surge from 53-degrees on the first of the month to 65-degrees by April’s close, falling just short of the 13-degree increase in “normal” daytime highs which occur in March.


Books close on a March ranked the coldest in 17 years


March 2013, a month in which Chicago’s average temperature came in at 32.6-degrees, finished 31st-coldest of the 143 Marches on the books here dating back to 1871.

But, in a unusual twist on spring’s typical temperature evolution trend as we move from winter to spring, March 2013 finished colder than December 2012′s observed 36.1 degree average.


In more typical years, March ends up warmer—NOT COLDER—than December by 10.2-degrees!


Gain of more than an hour of daylight is behind April’s tendency to warm


Reduced to basics, the seasonal increase in temperature with which we’re all familiar is driven by the sun.



Not only are its rays growing more direct as the sun tracks higher and higher across the sky each day, but days are continuing to lengthen—and will continue to do so in coming months. By April’s close, this month will see sunshine pour down on the metro area an additional one hour and 16 minutes beyond the more than 3 additional hours which have been added since the area’s shortest day which occurred as winter opened on Dec 21.


City’s 142-year observational record puts historic odds of a 70+ temp in the coming month at 99%; 80+degree odds at 56%  



More sunlight means improved chances for more frequent “warm” spells. Weather records here indicate 141 of the 142 Aprils for which we have official records—that’s 99% of them— have recorded a 70-degree or warmer high. At the same time, 80 of those 142 Aprils have generated an 80-degree or warmer reading, producing a historic probability of 56% that an 80°+ temp will occur before the end of this month.


15-month precipitation of 35.50″ running 7”+ below normal here; predicted wet pattern in coming weeks could put a dent in that deficit


A wet pattern is being predicted in the 6 to 10 day and 8 to 14 day time frames by a series of global computer forecast models out of a suite of meteorological centers around the world. Not the least among these forecasts are predictions from the National Weather Service’s “GFS” and “DGEX” models for significant rainfall next week.


The swath of heavy precipitation is to fall on the broad area of the nation’s Heartland still in the midst of drought.


Spring chill has slowed Lake Michigan-warming; water temps running 10-degrees behind a year ago


As a side-bar to our unseasonably chilly spring, Lake Michigan water temperatures are staging an abnormally slow seasonal temperature increase this year. The lake temperature off Chicago Monday was 41 degrees compared to 51 a year ago.