Building dome of heat to produce 90s over two thirds of the Lower 48 Tuesday

A RING OF FIRE PATTERN threatens sporadic thunderstorms; Chicago’s hottest temperatures predicted Thursday and Friday


Particulate and ozone levels have surged across the Chicago area Monday afternoon and the EPA now characterizes Chicago area air quality as “UNHEALTHFUL FOR SENSITIVE GROUPS”—which places air quality at LEVEL 3 on the EPA’s 6-LEVEL AIR QUALITY SCALE—the worst being level 6. The air quality at Madison, WI has even deteriorated to “UNHEALTHY.”


Southern Lake Michigan water temperatures—National Weather Service Chicago/Romeoville IL, 936 AM CDT, Monday, July 24, 2023

The Michigan City water temperature sensor is located at a water intake one mile offshore and 60 feet below the water surface. It is read every day of the year

  • It’s baaaack! In truth, it never completely left us. I’m talking about the smoke off those devastating Canadian wildfires, which continue to burn! We’ve awakened to smoky, hazy skies again in Chicago, across the Midwest and in a huge swath of Canada Monday. The smoke has never really completely departed the Chicago area—it’s grown denser as the new week gets underway
  • Air quality in Chicago is MODERATE with an air quality index reading of 76. But across the Upper Midwest north into Canada, air quality is UNHEALTHFUL.
  • Note the latest available North American Drought Monitor which offers an insight into the underlying dry conditions which have set the stage for the persistence and spread of fire.


  • Illinois leads all states across the U.S. for tornadoes in 2023, reports the National Weather Service’s Storm Prediction Center (SPC)—and heat and humidity are on the way threatening sporadic active “ring of fire” t-storm clusters later this week. The area is “outlooked” for potential severe weather Wednesday, and that may not be the only severe weather threat the back half of the coming week and into Saturday of the coming weekend.
  • The state tornado tally date is 119 twisters. That’s according to the latest National Weather Service Storm Prediction Center (SPC) tally. The next closest state, according to SPC, is Texas with 78 then Nebraska with 67. Both Iowa and Mississippi are tied for 3rd place to date in 2023 with 64 reported twisters filed with the Storm Prediction Center. (A shoutout to Kevin T. Sur, Public Information Officer (PIO), Illinois Emergency Management Agency and Office of Homeland Security (IEMA-OHS) for calling attention to the stats).
  • Heat and the sporadic threat of severe weather on the horizon for Chicago and sections of the Midwest—as early as Wednesday—the Wednesday-through-Saturday period is to see an anomalously strong jet stream take up residence across the Midwest on the northern flank of a dome of hot air, a heat dome likely to bring the Chicago’s hottest weather of the season while supporting sporadic “ring of fire” thunderstorm clusters—current thinking—storm coverage is not to be universal nor continuous—current estimate places storm prospects at 30 to 40% Wednesday; 12-28% Thursday and 31-38% Friday, like storm chances assessed this past Saturday.
  • Jet streams sweep the atmosphere at the northern periphery of hot air domes like the one to expand northward into the Midwest from mid week forward. Timing of these clusters is always challenging days ahead of time, and such storm clusters are critically important to the level of heat we end up seeing, since thunderstorms mix cooler air down to the surface.
  • But, even with outflows likely to temper the heat in some periods later in the week, our in-house average of the predicted temps off multiple computer model runs produced by 8 different models and a weather service “blended” model temp forecast. When corrected for the most recent set of temp model forecast errors, makes one thing clear: a period of steamy heat is on the way as the week proceeds.
  • Dew points, a measure of atmospheric moisture, are to surge to muggy Gulf Coast levels (in the 70s) Wednesday through Saturday and into Sunday morning. The temp/dew point combo from Wednesday forward through Saturday and into early Sunday is likely to produce a set of hottest, most humid “feeling” days of summer, 2023—potentially tempered on occasion by t-storm outflows.
  • The consensus of the late week model forecasts strongly suggests, barring a change in forecast trends since last week, is that Thursday and Friday will see an organized southwest wind flow likely to whisk heat and humidity back into the Chicago area in the wake of any thunderstorms which sweep Chicago, thus keeping heat and humidity dominant. Heat indices may well reach or exceed 100 degrees.
  • July rainfall has been varied across the greater Chicago area but is running well above normal at Chicago’s airports. O’Hare July 2023 rainfall is at 5.89”—210% the normal of 2.80” to date, while Midway’s July 2023 rainfall has been even more impressive, totaling 9.58”—312% the normal to date of 3.07.”
  • But, what’s interesting is if we examine total Chicago rainfall since April 1, Chicago’s precipitation tally is running 73% normal at O’Hare—with 10.98” of the normal 15.14” measure at the northwest side site.
  • Summer precip naturally varies widely, so the trend at O’Hare is not necessarily that of other sites in and around the Chicago area. But, it offers a gauge of the precip trend to date this growing season.


Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button