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  • Tim McGill

Mostly Blue Skies For The Blue Angels

Warm & Mainly Dry Thru Weekend

It will be an abbreviated version of the Chicago Air & Water Show this weekend but at least the weather should comply. Just a small chance for an afternoon or evening isolated shower or thunderstorm Friday. It should be mostly dry during the practice run between 10 a.m. and 2 p.m. tomorrow. The actual show will be from noon to 1 pm on Saturday and Sunday. Saturday has the best chance for rain but it should be mainly after 1 pm and Sunday looks dry.

Today won't be a bad day for flying, boating, running or walking too. Some late season summer steaminess is still in the air. Yesterday's high of 86° was the warmest in a week. It felt like the lower to even middle 90s in a few spots because of the higher humidity levels.

The HRRR Model has our highs again today in the middle to upper 80s for most areas. A breeze off the lake will hold highs in the upper 70s to near 80° along the lakefront. Average highs for today's date are around 83°. We could tag 90° southwest of the city.

The thicker smoke from western wildfires remains to our west and north but it is encroaching on us. The HRRR Model vertically integrated smoke forecast has relatively lower levels of smoke here again today but just west and north of us higher concentrations are expected. We should see an increase in smoke aloft Friday and Saturday. You might be looking up at the Blue Angels through a bit of haze this weekend.

The highest heat index or apparent temperature values on Wednesday were in the lower to middle 90s. Today's highs combined with dew points again well into the 60s and even up to 70° or more in a few spots should make it feel like 90° or hotter away from the lakefront.

A breeze will continue off of Lake Michigan through tomorrow. Highs will be held down again lakeside to near 80° or the lower 80s today and tomorrow.

Our best chance for an isolated shower or thunderstorm today and tomorrow is during the later afternoon hours. The lake breeze may provide enough lift of the moderately unstable air over land to spark spotty storms. Most of us will again be rain free through Friday.

The dew points climbed back well into the 60s and even into the lower 70s yesterday. They stay relatively high through Saturday and then drop Sunday to make for a more pleasant day. They drop more significantly by the middle and end to next week. A cooler and more comfortable pattern should start to settle in beginning Wednesday.

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 stay stuck in the "sticky" to "uncomfortable" levels through Saturday then drop to more pleasant levels Sunday. "Delightful" dew points are expected by Wednesday next week.

Highs will be near 90° today through Saturday. We cool into the lower 80s Sunday. The National Blend Of Models show a cooler pattern kicking in by the middle of next week as highs could even eventually slip back into the 70s a week from Friday.

I can't recall the last time I saw back to back long range temperature probability forecasts both favoring us for cooler than average temperatures. The 6-10 day forecast has outlooked Chicago for cooler than average temperatures overall from August 24th through August 28th. The longer range 8-14 day forecast also favors us for cooler than average temperatures overall from August 26th through September 1st. Our cooler pattern that kicks in towards the end of next week might stick around. 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.

Best Chance Of Rain Saturday

Some spots got some rain from hit or miss thunderstorms yesterday but not officially at O'Hare. Today will be the 9th straight day without measurable rainfall at O'Hare. 1.33" of rain has fallen there so far this month which is down 1.2" from average. O'Hare is now .33" below average since June 1st. Our best chance of rain comes with a cold front crossing through Saturday afternoon/evening but only about 40% coverage expected.

Our northern suburbs didn't get any appreciable rain this past week. I will have the latest analysis from the US Drought Monitor tomorrow and I suspect it will show the drought in our northern suburbs will have deepened a bit.

Chicago and most of our northern & northwest suburbs received between just 5% to 25% of average rainfall for the 7-day period ending yesterday morning.

Here is a recap of my Friday update on drought conditions based on numbers from last week's US Drought Monitor analysis:

It's another case of mostly good news from the latest US Drought Monitor analysis. The best news is that portions of Illinois in a severe drought dropped almost in half. 1.19% of the state is now in a severe drought (level 2 out of 4 levels) down from 2.19% last week. The bad news is 6.05% of the state is now in a moderate drought (level 1 out of 4 levels) up slightly from 6.00% last week. Northern Illinois is the only part of the state reporting drought conditions. There is more bad news. The portion of the state considered "abnormally dry" has increased to 15.20% from 10.99% last week.

The latest GFS model suggests a hit or miss shower or thunderstorm this afternoon with more of those possible Monday. This meteogram is showing the best chance for decent rainfall is coming late next Tuesday into Wednesday. It doesn't show any rain Saturday but I have it in the forecast because most of the models bring in scattered showers and thunderstorms that afternoon and evening.

The total precipitation forecast through Sunday afternoon from the GFS model suggests feast or famine rainfall. The range of rainfall would be between barely any in some of our northern suburbs to nearly four tenths of an inch west and south of the city. Not much of a feast but any rain would be welcomed. I think there may actually be locally heavier rainfall because of all the abundant moisture in the atmosphere. The character of the rainfall pattern though looks to be consistent with scattered showers and thunderstorms. Some places luck out and get decent rain while others go rain free.

Bad news for the our northern suburbs enduring the current drought. The long range rainfall forecasts are trending towards a drier pattern for the end of August and start of September. The latest 6-10 day forecast has the Chicago area favored for about average precipitation from August 24th through August 29th. The longer range 8-14 day forecast favors us for below average precipitation from August 26th through September 1st.

Most of the Midwest is also favored for above average rainfall in the long range forecasts too. The Midwest region's drought news is mixed with the latest analysis. The good news is the area in both the moderate and severe drought levels dropped slightly. The bad news is the area in an extreme drought increased slightly and for the first time a portion of the region slipped into an exceptional drought, the highest level.

The west region saw a a slight decrease in their extreme and exceptional drought area, the two highest categories of drought. The area in the two lowest levels of drought, moderate and severe, increased slightly. More than 95% of the west is in some level of drought and just over a quarter of it is in the worst level of drought, the exceptional category.

Here is my 7 day forecast:

Today: Partly to mostly sunn, isolated shower/t-storm? High: 87 (80 along lakefront)

Friday: Patchy a.m. fog, partly to mostly sunny Low: 72 High: 88 (82 lakeside)

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: 85 (cooler lakeside)


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