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  • Tim McGill

End Of Above Average Streak In Sight

16 Straight Days Above Average

Yesterday's high of 77° at O'Hare marked the 16th straight day with above average temperatures. That streak should continue through at least Thursday and possibly to Friday. Cooler air will arrive just in time for the weekend when it will actually feel like fall.

It was a soggy start to the week on Monday with O'Hare picking up .75" of rain. That is the most in a single day since late August. The storms that brought that rain produced wind gusts over 60 mph in spots. Strong winds brought down some large trees on the city's north side. A tree fell across a truck near the intersection of Cullom and Paulina.

Average highs for today's date are around 65°. After a few spotty sprinkles or showers early on this Tuesday we will see enough sun mixed with clouds to push our highs into the lower 70s. The GFS Model has our highs this afternoon between 70° to 74°.

If you are waiting for more cool and crisp fall weather with more typical temperatures for this time of the year, then Saturday is your day. The GFS Model has our highs Saturday falling into the upper 50s to near 60°. It could be the coolest day here in over four months.

The GFS Model temperature anomaly forecast for Saturday afternoon has our temperatures between 2° to 6° below average. The average high for Saturday is 63°.

We still get a few more days with highs in the 70s before that cooler air arrives. Some strong breezes out of the southwest today and more southerly tomorrow will help push our highs into the lower 70s both today and Wednesday.

The next best chance of rain comes late Wednesday into Wednesday night. Some of the storms bringing this rain could be severe. More on that below.

Looking Longer Range At Mild Pattern

It has been a rather mild month so far. O'Hare is now running 12° above average. There are a few more typical fall days in the forecast with highs sliding back into the lower 60s this weekend. The National Blend Of Models has the coolest day of the next eleven arriving on Saturday. Parts of northern Illinois may fail to climb out of the 50s during the day. 60s for highs could stick around through all of next week.

The signal isn't particularly strong but the longer range temperature outlooks both favor us for a warmer than average pattern. The 6-10 day outlook has us favored for above average temperatures overall from October 17th through October 21st. The longer range 8-14 day forecast also favors us for above average temperatures overall. It covers the period from October 19th through October 25th. Average highs for this period are in the upper 50s to lower 60s.

The even longer range temperature anomaly forecast keeps the overall mild pattern going into next month. The longer term 30 day temperature anomaly forecast still has all of the Midwest and most of the country outlooked for above average temperatures overall all the way through the first week of November. We are outlooked to be between 4° to 6° above average overall for the period from October 10th through November 10th. The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members The model tries to give an idea of the amount of uncertainty in a forecast by running an ensemble of multiple forecasts which are each tweaked a bit with their initial conditions.

Catching Up A Bit On Rainfall

O'Hare now has a surplus of .38" of rain above average for the month of October after three quarters of an inch of rain fell there on Monday. O'Hare is still down 1.58" of rain below average since the start of September.

More rain is needed to put a dent in the drought impacting northern Illinois. The most recent US Drought Monitor analysis was released last Thursday.

The areas in a moderate drought (level 1 our of 4) and severe drought (level 2 out of 4) increased slightly from the previous week while the area in an extreme drought (level 3 out of 4) remained unchanged.

Here is a summary of the impacts the ongoing drought is having on northern Illinois from the National Weather Service:

Volunteer observers across far northern Illinois indicate much lower then typical stream flows on area creeks and rivers, particularly along Beaver Creek and the Kishwaukee River.

Reports also indicate that lawns have gone dormant and there has been some stress to the trees. Few impacts to agriculture have been received recently, though the dry conditions and stressed crops have resulted in an early start to the harvest season across northern Illinois. Data available from the Illinois State Water Survey, USGS, and NCEP indicate that soil moisture, groundwater, and surface water levels remain below normal.

The drought news for the entire Midwest was mostly good. The areas in a moderate, severe and extreme drought all decreased at least slightly. The area considered abnormally dry increased slightly.

The GFS model's meteogram for O'Hare shows a few spotty sprinkles or showers possible during the early morning hours today but a better chance for rain is coming Wednesday night into early Thursday morning. Another round of rain is suggested for late Friday into early Saturday.

The GFS model's total precipitation forecast through the weekend. Most of the area is forecast to receive rainfall in the range of about a quarter of an inch to nearly three quarters of an inch with parts of northern Indiana receiving more than an inch.

The Storm Prediction Center has placed our northern suburbs are in a marginal risk (level 1 out of 5) area for severe weather late Wednesday into early Thursday morning. The greatest threat would be damaging winds but an isolated tornado can't be ruled out.

A marginal risk is level 1 out of 5 possible risk levels. It is the low end of the risk categories but means "an area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity".

The longer range precipitation outlooks suggest a relatively dry pattern for the middle to latter part of the month. The latest 6-10 day forecast has the Chicago area favored for below normal rainfall from September October 17th through October 21st. The longer range 8-14 day forecast has us outlooked for below average precipitation from October 19th through October 25th.

Here is my 7 day forecast:

Today: Spotty sprinkles early then becoming partly to mostly sunny High: 72

Wednesday: Mostly cloudy, breezy, sct. showers/t-storms possible late Low: 57 High: 73

Thursday: Shower possible early, mostly cloudy, sct. pm shower possible Low: 61 High: 71

Friday: Partly to mostly cloudy, sct. showers possible Low: 55 High: 67

Saturday: Mostly sunny, cooler Low: 48 High: 59

Sunday: Mostly sunny Low: 46 High: 63

Monday: Mostly sunny Low: 47 High: 67


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