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  • Tim McGill

Another Heat Wave To Roll In

An Unremarkable July


We had a few rather hot days last month but overall it was 1° below average. No records were set during the month. We hit 90° or warmer five times in July. We average about seven 90° days for the month. 18 of 31 days were below average. Just 1.9" of rain fell which is 1.81" below average.




August Set To Get Steamy


August has started out 6° below average but another mini-heatwave is ready to roll in this weekend and linger into early next week.

The HRRR Model has our highs today getting closer to the average of 84° for today's date. Highs today should climb to just above 80° but a breeze off the lake will keep it cooler lakeside with highs there in the upper 70s.



Slowly but surely both the heat and humidity will build and by the weekend our highs should climb to near 90°.


The heat will peak early next week. The combination of heat and humidity on Monday will make it feel like 100° or hotter for most of us.



Today and tomorrow will be more seasonably warm. Highs today climb to just above 80° and tomorrow they make it into the middle 80s. Humidity levels are held in check with dew points in the 50s during this timeframe. A breeze off the lake both today and tomorrow will keep it cooler at the lakefront. Only very small chances of rain with an isolated shower possible both days.



Our dew points start to surge Thursday and climb through the weekend into early next week. Dew points are the preferred measure of moisture in the atmosphere for meteorologists. They remain in the 50s through most of tomorrow then start to climb into the 60s Thursday and end up in the 70s by early next week. So we climb from comfortable levels of humidity today to oppressive levels by Monday.



The National Blend Of Models has highs near 90° or above from Friday into Wednesday next week. Monday may end up being the hottest day in terms of both temperatures and humidity levels.



More hazy sunshine mixed with clouds today. The HRRR Model vertically integrated smoke forecast keeps the wildfire smoke from the west and Canada around most of today. The net effect of wildfire smoke is to keep temperatures a degree or too cooler depending on its concentration.



Here are some articles related to wildfire smoke that you may be interested in:



There is fairly high confidence that this weekend will be hot and humid and the longer range temperature probability forecasts suggest steamy weather could linger through next week. The 6-10 day forecast has outlooked Chicago for above average temperatures overall from August 8th through August 12th with our area within highest probability level. The longer range 8-14 day forecast continues to favor us for above average temperatures overall from August 10th through August 16th. Average highs are in the lower to middle 80s for the start to August.



The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts keeps us warmer than average through nearly the end of August. The forecast for the week ending on August 20th has us outlooked for above average temperatures. The forecast for the week ending on August 27th favors us for above average temperatures overall too.




Northern Suburbs Still Need Some Rain


July ended up 1.81" of rain below average and we are now down 6.42" inches below average since the start of spring. August is running .30" below average.


Here is a recap of the latest drought analysis that I posted last Friday:


The latest analysis from the US Drought Monitor shows absolutely no change in drought conditions for northern Illinois from the previous analysis a week ago. The area of Illinois in a moderate drought (level 1 out of 4) remains unchanged at 7.17%. The area of the state in a severe drought (level 2 out of 4) remains unchanged at 2.31%.

It has been a fairly dry end to the month of July so far. Rainfall over a two week period that ended on July 28th shows the most parched portions of Illinois were out of luck when it came to rainfall. Parts of Lake and McHenry counties picked up just 10% to 25% of average rainfall during the period. Most of the northern third of the state was well below average in terms of rainfall.



The latest GFS model suggests a spotty shower or thunderstorm is possible Saturday and Sunday but the chances are fairly low. Most of the weekend should be dry. Some scattered showers and thunderstorms are possible next Tuesday and Thursday too. Overall this is a fairly dry pattern though for the next ten days.



I ran the GFS model total rainfall forecast through Monday morning and the results still don't offer much hope for significant rainfall to put a dent in our northern suburbs drought. The range of rainfall expected varies for a couple tenths of an inch to nearly a third of an inch. We average about .65" of rain for this period.




The Midwest region saw improvements in one drought level but more discouraging news for two others. The area in a moderate drought fell .18% to 27.33% for the state. The area in a severe drought increased .82% to 16.74%. The area in an extreme drought increased .60% to 3.73%.


The west is still suffering from a serious drought that has expanded in two out of the four drought levels and has shrunk in two others. Both the moderate and severe drought area has expanded slightly while the extreme and exceptional drought areas have decreased at least slightly. The most substantial shift was in the highest drought level. The area in an exception drought fell from 28.03% to 24.63%.



Once again both of the long range precipitation probability forecasts have us outlooked for above average rainfall. This would suggest a more active pattern developing for next week. The latest 6-10 day forecast has the Chicago area favored for above average precipitation overall from August 8th through August 12th. The longer range 8-14 day forecast also favors us for above average rainfall from August 10th through August 16th.




Here is my 7 day forecast:


Today: Partly to mostly sunny, isolated shower possible High: 81 (78 lakeside)


Wednesday: Mostly sunny, warmer Low: 62 High: 83 (cooler lakeside)


Thursday: Partly to mostly sunny Low: 64 High: 85

Friday: Partly/mostly cloudy, sct. t-storm possible Low: 67 High: 83


Saturday: Partly to mostly sunny, sct. shower/t-storm possible Low: 69 High: 89


Sunday: Partly/mostly sunny, sct. shower/t-storm possible Low: 69 High: 90


Monday: Partly to mostly sunny, sct. shower/t-storm possible Low: 72 High: 92


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