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  • Tim McGill

Weekend Forecast & Drought Update

Steamy Through Saturday


Most of us agree that we need some rain and a break from the high heat and humidity. We will get both at some point this weekend. The best chance for rain will be Saturday afternoon and Sunday should bring relief from our steamy summer pattern we have been in lately.


The rain may impact the abbreviated version of the Chicago Air & Water Show on Saturday but most of it will come later in that afternoon. The Blue Angels will put on a show between noon and 1 pm Saturday and Sunday. A scattered shower or thunderstorm is possible Saturday but the greatest chance for rain will start around or just after 2 pm and last through late in the afternoon. Sunday's show should be set against blue skies.


Mostly blue skies for the Blue Angels practice today between 10 a.m. and 2 p.m. today. There is only a slight chance for an isolated shower or thunderstorm popping up.


Thursday's high of 88° was the warmest in over a week. Today should be just as hot or even a degree or two hotter. The HRRR Model has our highs topping out near 90° today. A breeze off the lake will hold highs in the lower 80s along the lakefront. Average highs for today's date are around 82°. The high humidity will make it fell like at least the lower 90s.



We have been spared the thicker wildfire smoke this week so far but higher concentrations are expected today. You may notice more haze in our skies today. The HRRR Model vertically integrated smoke forecast actually brings in some smoke aloft from the north and even northeast. The thicker smoke (depicted in orange) should remain north and northeast of Chicago.



The heat index or apparent temperature values today should reach into the lower 90s and might even make it into the middle 90s on Saturday.


Nature's air conditioner will bring some relief from the heat today along the lakefront with a breeze off of Lake Michigan. Highs at the beaches will be held down in the lower 80s.


There is a slight chance for an isolated shower or thunderstorm this afternoon. The best chance of rain this weekend will be during the afternoon on Saturday. Expect about 40% coverage so this will not be a washout. There will be dry hours tomorrow and Sunday should be completely dry.



The dew points hover around 70° or even soar into the lower 70s today and Saturday before dropping to more pleasant levels on Sunday. It will be a steamy start to next week but relief comes before the week is over. Dew points jump back up Monday and then gradually decline through next week.



Relative humidity is one way to express the amount of water vapor in the air but dew points are the preferred measurement of moisture in the air for meteorologists like me. We are stuck at least in the "sticky" to "uncomfortable" dew point levels through Saturday before dropping to more "pleasant" levels Sunday.



Highs will be near 90° today and tomorrow. A cold front comes through late Saturday and then we fall into the lower 80s Sunday. The National Blend Of Models has us soaring back to near 90° Monday through Wednesday next week before falling back into the lower 80s by the end of the week.



The long range temperature probability forecasts start us off above average and then drop us to around average by the start of September. The 6-10 day forecast has outlooked Chicago for above average temperatures overall from August 25th through August 29th. The longer range 8-14 day forecast favors us for around average temperatures overall from August 27th through September 2nd. Average highs are in the lower 80s for this part of August.



The even longer range Subseasonal Experiment (SubX) temperature anomaly forecasts suggest a warmer than average end to August and start to September. The forecast for the week ending on September 3rd has us outlooked for above average temperatures. The forecast for the week ending on September 10th also favors us for above average temperatures overall. It takes a close inspection of both graphics to see the pixel representing the Chicago area is yellow. That corresponds to a temperature anomaly of .15° to .45° Celsius above average.








More Rain Needed


Just a few spots got some rain on Thursday but most of us missed out. Only an isolated shower or thunderstorm possible today but better chances for rain come tomorrow. Thursday was the 8th straight day without measurable rainfall at O'Hare. 1.33" of rain has fallen there so far this month which is down 1.33" from average. O'Hare is now .46" below average since June 1st.


Most of northern Illinois didn't see any measurable rain during the seven day period from August 13th through the 19th. Zero to 5% of average rainfall fell during the period.

So it is no surprise we got mostly discouraging news from the latest US Drought Monitor analysis. The only good news is the portion of Illinois in a severe drought (level 2 out of 4 levels) dropped from 1.19% last week to .79% this week. The bad news is 7.33% of the state is now in a moderate drought (level 1 out of 4 levels) up from 6.05% last week. Northern Illinois is the only part of the state reporting drought conditions. More bad news. The portion of the state considered "abnormally dry" has increased to 15.42% from 15.20% last week.



The latest GFS model suggests some scattered showers and thunderstorms Saturday afternoon and then a more active pattern emerging next week. There could be an isolated shower or storm on Monday but it looks more promising for some precipitation just beyond then. This meteogram is showing periods of showers and thunderstorms late Tuesday through the following weekend.



The total precipitation forecast through Sunday afternoon from the GFS model squeezes out just a couple tenths of an inch of rain to about a quarter of an inch. There could be some locally heavier amounts with thunderstorms though. Not exactly drought busting rainfall.



Not much hope for more help with the drought in the longer range rainfall forecasts. The latest 6-10 day forecast has the Chicago area favored for below average precipitation from August 25th through August 30th. The longer range 8-14 day forecast also favors us for below average precipitation also from August 27th through September 2nd.



Most of the Midwest is also favored for below average rainfall in the long range forecasts. The Midwest region's drought news is all bad with the latest analysis. There was at least a small increase in every level of drought for the region.



The west region some minor good news with this latest analysis. The areas in a moderate, severe and extreme drought all saw at least a small decrease. Unfortunately the area in the most dire drought category saw an increase. 25.71% of the region is in an exceptional drought. That is up from 25.35% last week. More than 95% of the west is in some level of drought.





Here is my 7 day forecast:


Today: Partly to mostly sunny, hot, isolated shower/t-storm? High: 89 (82 along lakefront)


Saturday: Partly to mostly cloudy, pm sct. showers/t-storms Low: 71 High: 88


Sunday: Mostly sunny, less humid Low: 68 High: 83 (78 lakeside)


Monday: Partly/mostly sunny, sct. shwr/t-storm possible Low: 68 High: 90 (cooler lakeside)


Tuesday: Partly/mostly sunny, sct. shwr/t-storm possible Low: 71 High: 89 (cooler lakeside)


Wednesday: Partly/mostly sunny, sct. shwrs/t-storms Low: 72 High: 88


Thursday: Partly/mostly sunny, sct. shwr/t-storm possible Low: 72 High: 83 (cooler lakeside)


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