ASK TOM: Has Chicago's high and low temperature ever been the same?

Dear Tom,

On how many days in Chicago weather history have the day’s high and low temperatures been the same? That is, the temperature did not change at all?

– Doc. B, U.S. Navy


Dear Doc,

Since 1870, it has happened once. Chicago’s weather is always in a state of flux, and rarely do temperatures hover at exactly the same value for more than a few hours. That’s the reality we live with.

On very rare occasions, though, when the progression of weather systems across the Midwest has greatly slowed and Chicago finds itself with high humidity, a foggy and densely overcast sky, and practically no wind, the temperature can remain absolutely stationary. Such was the case for a record 30 consecutive hours from 9 p.m. Feb. 5, 1942, to 3 a.m. Feb. 7, when Chicago’s temperature sat unchanging at 35 degrees.

Lake effect snow showers to flirt with shoreline areas of Wisconsin, Illinois and Indiana

We’ve certainly witnessed lake-effect snow bands doing their thing in recent days. Their bursts of snowfall tend to be incredibly localized—rapidly whitening one area while completely avoiding others.

The limited real estate covered by the snows generated in “lake-effect” scenarios can be striking.  But so can the amount of snow which is generated at times in amazingly small areas.

The selective nature of lake snows was on display for all to see in the Evanston, Skokie and Morton Grove areas Thursday evening. The fluffy, silver-dollar-sized snowflakes reported in that region of the metro area deposited comparatively quick 3 to 5” accumulations—even as the official O’Hare weather observation site, not more than 10-15 miles away, only picked up 0.3” of snow. Midway’s take of the lake-effect snow “pie” was even smaller, having measured a miniscule 0.2” accumulation.

High resolution computer models, which aid us in predicting lake snows, suggest concentrated clusters of snowfall will flirt with shoreline areas from eastern Wisconsin south into extreme northeast Illinois and parts of northwest Indiana from time to time Saturday. Converging winds, responsible for producing these snows, may set the stage for brief bursts of significant snowfall likely to be limited to highly localized areas. A quick dusting to as much as an inch or two may fall with some of the heavier snow showers while other sections of the Chicago area escape with just flurries.



Friday’s 0.3” of snow does little to boost lowest seasonal snow tally in 69 years; total of 0.7” just 8 per cent of normal!


Friday’s fresh 0.3-inch accumulation of snow at O’Hare boosted Chicago’s official seasonal snow tally to 0.7”—just 8 per cent normal and nearly 8” off the typical full season tally by this date.


A 308th day at/above freezing ties a 134-year record for most consecutive daytime highs at/above 32 Saturday; record could fall Sunday


Evidence of this winter’s remarkably “un-wintry” ways continues to accumulate.  We’ve covered the paltry snow situation. The failure of truly cold air to reach the area is yet another of the emerging stories in this very “un-wintry” winter of 2012-13 to date.

Saturday’s predicted 33-degree high will mark the 308th consecutive day high temperatures have failed to remain below freezing. That’s a development which will tie a 134-year-old record for the most back-to-back days with daytime temperatures at or above freezing. The failure of temperatures to fall short of 32-degrees Sunday would set a new record.



Overnight storm deposits fresh snow cover in already hard-hit areas of downstate Illinois and Indiana


The second storm in less than a week—and the Midwest’s third storm of the past two weeks—swept downstate Illinois and Indiana overnight depositing another 2 to 6” of snow.

NOAA reported Friday that 64.5% of the Lower 48 was under a cover of snow—the largest national snow-pack in nearly two years.

Last year’s unimpressive 29% snow coverage across the 48 contiguous U.S. states was just 39% of that tally.



Several forecast models hint at New Year’s Eve snow threat


It’s not a forecast yet carved in stone.  But, several of our computer forecast models develop snow here late Monday and Monday night—suggesting a potentially snowy New Year’s Eve. That wouldn’t be without precedent. One in four Chicago New Year’s Eves have registered measurable snow.


Season’s coldest air to hit mid-week—but only for several days


Winter’s chilliest temps to date may put in an appearance next week. The arctic air would follow several frontal systems expected to sink into the Lower 48 in coming days.  The good news is the overall pattern appears progressive, so the chill isn’t likely to linger for long.

Winter slowly tightening its grip on city

So far Chicago’s winter has been a piece of cake with little snow and cold. With the exception of a few lakeside locations, snowfall has been minor with the season’s snowfall total in most areas still less than one inch, well below the 9.0 inches typical to date. The city has not recorded a subfreezing high since a 27 degree high on February 25, and should tie the record for the city’s longest such stretch of 308 days Saturday.


Colder days ahead

As the end of the year approaches, colder weather is making inroads into the area and snowfall, while not heavy is occurring with increasing frequency. Another round of lake-effect snow should whiten lakeside counties Saturday while a developing weather system threatens a New Year’s Eve snowfall, especially for the south portions of the Chicago area. The coldest weather of the season will start the New Year with forecast highs in the teens and lower 20s and lows in the single-digits and teens.

ASK TOM WHY: What is the longest interval between snows of at least 3 inches? And where do we stand this year for that?

Dear Tom,

So we finally had “measurable snow” and set a new record for longest interval without snow, but it didn’t amount to much. What is the longest interval between snows of at least 3 inches? And where do we stand this year for that?

— Brad Johnson


Dear Brad,

Chicago’s first measurable snow of the season was a puny 0.2 inches on Dec. 20., but sufficient to set a new city record for the longest stretch without measurable snow — 290 days.

Snow storms bringing heavier snow totals occur less frequently and the intervals between them are greater. As of Dec. 28, it’s been 308 days since Chicago booked a storm of at least 3.0 inches (3.5 inches on Feb 24, 2012), but that’s no threat to the record between storms of at least 3.0 inches. That record stands at 1,043 days — 2.9 years — from April 5, 1920 through Feb. 11, 1923.