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McHenry, IL Weather
Current conditions
Observed at Chicago/Waukegan Regional Airport · 28 min ago
Forecast
10-day-
Tonight
Patchy fog after 3am. Mostly clear, with a low around 45. Wind around 0 mph.
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Thursday
Patchy fog before 9am. Sunny. High near 72, with temperatures falling to around 68 in the afternoon. Northeast wind 0 to 5 mph.
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Thursday Night
Partly cloudy, with a low around 46. East northeast wind 0 to 5 mph.
National Weather Service forecast updated 5 hrs ago.
Hourly
Hourly forecast- Now54°
- 10 PM52°
- 11 PM50°
- Thu12 AM48°
- 1 AM48°
- 2 AM48°
- 3 AM48°
- 4 AM47°
- 5 AM46°
- 6 AM46°
- 7 AM46°
- 8 AM48°
- 9 AM52°
- 10 AM60°
- 11 AM64°
- 12 PM68°
- 1 PM70°
- 2 PM71°
- 3 PM71°
- 4 PM70°
- 5 PM68°
- 6 PM65°
- 7 PM58°
- 8 PM54°
10-day forecast
Details- TodayOct 21Sunny45°72°
- ThuOct 22Patchy Fog then Sunny46°72°
- FriOct 23Mostly Sunny48°71°
- SatOct 24Partly Sunny50°70°
- SunOct 25Partly Sunny50°72°
- MonOct 26Partly Sunny15%47°66°
- TueOct 27Slight Chance Rain Showers24%44°61°
- WedOct 28Cloudy0.13 in47°63°
- ThuOct 29Rain0.65 in38°59°
- FriOct 30Sunny36°54°
Days after the National Weather Service's seven are MET Norway's outlook, a computer model with no forecaster's review.
Radar
Full mapWeather news near McHenry
More weather news-
Dense fog advisory issued for parts of Chicago area with with near-zero visibility on roadsParts of the Chicago area are under a dense fog advisory Tuesday morning, with visibility close to zero leading to dangerous driving conditions for the morning commute. The advisory, issued for Central Cook, Lake…
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First frost of season possible Saturday morningA group of people cross the La Salle Street Bridge in The Loop on Feb. 4, 2026. Temperatures could dip below freezing early Saturday morning in areas outside Cook County, bringing a brief interruption to the Chicago…
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Chicago weather: Cloudy, rainy Friday ahead of warmer, sunnier weekendKaitlin Cody has your Chicago weather update! CHICAGO - A cloudy and damp day will give way to a much sunnier stretch across the Chicago area. Friday will bring cloudy skies and temperatures in the low 50s. Rain could…
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‘Coldest night of the season:' Frost advisory, freeze warning issued for parts of Chicago areaTemps drop below the freezing mark for parts of the area Saturday morning Here it comes, Chicago: Frost advisories and freeze warnings were issued for parts of the area, with temperatures dropping into the 30s overnight…
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Tropospheric Conditions Affect UHF & VHF Signals Across the CoastOften in the spring and fall television and radio signals on the MS Gulf Coast can be adversely affected by a meteorological event known as tropospheric ducting. Here is a technical explanation for what is causing…
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Mostly cloudy and dry today, with soggy weather returning ThursdayMostly cloudy and dry today, with a soggy weather returning Thursday WIFR ROCKFORD, Ill. (Rockford News First) - Not much precipitation fell earlier this morning, with Rockford picking up about .10″of rain. Temperatures…
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Another beautiful day ahead for Central IllinoisDECATUR, Ill. (WAND) – If you’re looking for a reason to get outside, Tuesday is your day. A high-pressure system settling over the Midwest is bringing abundant sunshine and calm winds to Central Illinois, with…
- Central Illinois Winter Weather Outlook
The winter weather outlook for central and southeast Illinois has been released, and a detailed summary is available at this link. Some of the highlights: Current Conditions Latest Observations Daily Climate Maps…
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One of the year’s most pleasant weather stretches arrives in Central IllinoisDECATUR, Ill. (WAND) – A beautiful stretch of sunshine and mild temperatures is settling into the region, and it’s the perfect time to get outside and enjoy it. High pressure is taking control of the Midwest, locking in…
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A great week ahead for Central IllinoisWAND DECATUR, Ill. (WAND) – A wonderful weekend across Central Illinois carries into the start of the workweek. Overnight lows dip back into the upper 30s tonight with a small risk for patchy frost, though coverage will…
Air quality
Acceptable. Unusually sensitive people should consider limiting prolonged outdoor exertion.
Forecast
- WedModerate
- ThuModerate
- FriModerate
North and West Suburbs (Chicago), IL reporting area · 1 hr ago. Data from AirNow (EPA and its state, local and tribal partners); preliminary and subject to change.
Sun & moon
Almanac
MonthlyLake Geneva Wwtp, records since 1945. Normals 1991–2020. Data from NOAA's Regional Climate Centers (ACIS).
Nearby
- Elgin 33 km
- Kenosha 46 km
- Waukegan 35 km
- Racine 59 km
- Arlington Heights 36 km
- Evanston 58 km
- Schaumburg 37 km
- Palatine 31 km
- Skokie 55 km
- Des Plaines 46 km
- Mount Prospect 40 km
- Wheaton 54 km
Forecasters' discussion
From the National Weather Service office in LOT, issued 3 hrs ago
Key Messages
- The dry and unseasonably mild weather will continue through the upcoming weekend.
Discussion
Issued at 136 PM CDT Wed Oct 21 2026
An anomalously strong mid-level ridge over the central CONUS will anchor omega blocking across much of North America over the next several days. Meanwhile, an elongated surface ridge extending from the Lower Mississippi River Valley to the Canadian Maritimes is in the processes of congealing with another expansive high pressure shifting toward the Upper Great Lakes. As a result, quiet weather with unseasonably warm conditions will continue through the upcoming weekend. As was observed the past few mornings, generally clear skies and light/calm winds should promote shallow fog across primarily interior northern Illinois late tonight through sunrise Thursday.
The blocking pattern will slowly break down early next week as the ridge flattens and a southwestern upper-level low begins to meander toward the central CONUS. A series of smaller troughs on the periphery of a developing longwave trough across the north Pacific and western Canada will eventually pick up the southwestern low. Consensus guidance suggests that the influence of the low on our area could occur as early as Monday night, but more likely Tuesday and Wednesday. Cooler and more seasonable conditions would accompany this system.
Kluber
Aviation
Issued at 641 PM CDT Wed Oct 21 2026
Main aviation forecast concern is the potential for patchy IFR/LIFR fog to develop mainly northwest of Chicago early Thursday morning.
Surface high pressure ridge has shifted east of the area across lower MI/IN early this evening. Light south-southwest surface winds at the terminals are expected to quickly become light/variable or just calm early this evening, though there may be a brief (1-hour)period of light east winds at ORD/MDW/GYY as a weak lake breeze decays. The pressure gradient will remain weak into Thursday, keeping winds light/variable through the morning before becoming light (5-6 kts) northeast and eventually east in the afternoon/evening.
Clear skies and light/calm winds tonight will allow for ideal radiative cooling conditions, allowing shallow fog to develop in spots once again. This appears most likely across southern WI/northeast IA and far northern/northwest IL KRFD) where surface dew points remained in the mid-upper 40s during peak mixing Wednesday afternoon. While guidance is not too aggressive with lower visibilities, have maintained a 2SM IFR tempo and MIFG in the KRFD TAF, and will monitor overnight for tactical lower vsbys. The drier low-level airmass to the southeast looks to be less conducive to fog development with southeastward extent. Have maintained a 3SM MIFG tempo at DPA, with VFR conditions for the other Chicago area terminals.
Ratzer
Lot Watches
IL...None. IN...None. LM...None.
Forecasts, observations and alerts in the United States come from the National Weather Service (NOAA); radar from NOAA's Multi-Radar Multi-Sensor system; satellite imagery from NASA's Global Imagery Browse Services (GIBS) and NOAA's GOES satellites; the map from the U.S. Geological Survey's National Map; air quality from AirNow (EPA and its partners); hurricane information from the National Hurricane Center; climate normals and records from NOAA's Regional Climate Centers (ACIS). Forecasts outside the United States and the UV index: MET Norway (CC BY 4.0); observations outside the U.S.: airport reports via NOAA's Aviation Weather Center. Place names: GeoNames (CC BY 4.0). Data are copied on a schedule and may lag the sources; for warnings that affect your safety, follow your local National Weather Service office and emergency officials. Weather news is drawn from the 4Search index and reflects what the press published. Terms of use.