Algonquin, IL Weather

McHenry County9:07 AM CDT42.17°N, 88.29°WElevation 741 ft
Dense Fog Advisory until 10:00 AM Tue

Current conditions

Fog
43°
Fog
Feels like 43°
High 68°·Low 42°
WindCalm
Humidity93%
Dew point41°
Pressure30.40 inHg
Visibility0.2 mi
Cloud cover28%
UV index1 Low
Sunrise7:12 AM
Sunset6:05 PM

Observed at Chicago / West Chicago, Dupage Airport · 1 hr ago

Forecast

10-day

  • Today

    Patchy fog before 8am. Sunny. High near 68, with temperatures falling to around 65 in the afternoon. East wind 0 to 5 mph.

  • Tonight

    Patchy fog after 4am. Mostly clear, with a low around 42. East southeast wind 0 to 5 mph.

  • Wednesday

    Patchy fog before 8am. Sunny. High near 70, with temperatures falling to around 67 in the afternoon. West southwest wind 0 to 5 mph.

National Weather Service forecast updated 3 hrs ago.

Hourly

Hourly forecast
  1. Now Mostly Sunny 51°
  2. 10 AM Sunny 57°
  3. 11 AM Sunny 61°
  4. 12 PM Sunny 64°
  5. 1 PM Sunny 66°
  6. 2 PM Sunny 67°
  7. 3 PM Sunny 68°
  8. 4 PM Sunny 68°
  9. 5 PM Sunny 65°
  10. 6 PM Clear 60°
  11. 7 PM Mostly Clear 56°
  12. 8 PM Mostly Clear 53°
  13. 9 PM Mostly Clear 51°
  14. 10 PM Mostly Clear 49°
  15. 11 PM Mostly Clear 48°
  16. Wed12 AM Mostly Clear 47°
  17. 1 AM Partly Cloudy 47°
  18. 2 AM Mostly Clear 46°
  19. 3 AM Partly Cloudy 45°
  20. 4 AM Patchy Fog 44°
  21. 5 AM Patchy Fog 43°
  22. 6 AM Patchy Fog 42°
  23. 7 AM Patchy Fog 42°
  24. 8 AM Mostly Sunny 45°

10-day forecast

Details
  1. TodayOct 20 Patchy Fog then Sunny Patchy Fog then Sunny42°68°
  2. WedOct 21 Patchy Fog then Sunny Patchy Fog then Sunny45°70°
  3. ThuOct 22 Sunny Sunny47°70°
  4. FriOct 23 Sunny Sunny47°67°
  5. SatOct 24 Mostly Sunny Mostly Sunny51°68°
  6. SunOct 25 Partly Sunny Partly Sunny48°69°
  7. MonOct 26 Mostly Sunny then Slight Chance Rain Showers Mostly Sunny then Slight Chance Rain Showers15%44°65°
  8. TueOct 27 Cloudy Cloudy43°55°
  9. WedOct 28 Cloudy Cloudy42°52°
  10. ThuOct 29 Sunny Sunny40°53°

Days after the National Weather Service's seven are MET Norway's outlook, a computer model with no forecaster's review.

Radar

Full map
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Air quality

58
Moderate
Fine particles (PM2.5)

Acceptable. Unusually sensitive people should consider limiting prolonged outdoor exertion.

Forecast

  • TueModerate
  • WedModerate
  • ThuModerate

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

Sunrise 7:12 AM
Sunset 6:05 PM
Daylight 10 h 52 min (−2 min 41 s tomorrow)
Waxing Gibbous · 69% lit
Moonrise 3:26 PM Moonset 1:05 AM
Full moon Oct 26 New moon Nov 9

Almanac

Monthly
Normal high / low58° / 40°
Record high78° (1971)
Record low20° (1964)
Wettest1.81 in (1995)
Yesterday61° / 40°, <0.01 in
Month to date2.55 in (normal 2.12 in)

Barrington 3sw, records since 1962. Normals 1991–2020. Data from NOAA's Regional Climate Centers (ACIS).

Nearby

Forecasters' discussion

From the National Weather Service office in LOT, issued 2 hrs ago

Key Messages

- Some ground fog may develop within 10-15 miles of Lake Michigan during early morning hours the next few days. Any fog would then quickly dissipate after sunrise.

- An extended period of dry and above to much above average temperatures is expected through the upcoming weekend.

Discussion

Issued at 154 AM CDT Tue Oct 20 2026

No significant weather is expected through the upcoming weekend with above to much above average temperatures each day. Generally light winds should allow weak lake breezes to form each of the next several afternoons, but only result in slightly cooler conditions right near the lake. A modest increase in moisture in the wake of the afternoon lake breezes could allow for some ground fog to form during the early morning hours the next few days. Otherwise, look for mostly sunny conditions for the remainder of the work week.

- Borchardt/Izzi

Aviation

Issued at 620 AM CDT Tue Oct 20 2026

Key Aviation Messages for the current TAF period:

- Patchy fog, locally dense, expected through sunrise today for Chicago terminals north of a KARR to KMDW line

- Another chance for fog tomorrow morning for terminals closer to the lake

A locally dense fog bank is slowly moving west-southwest through northeastern Illinois this morning. The densest portion of this fog dropped visibilities at KORD down to 1/8SM. This fog is expected to impact terminals north of a KARR to KMDW line. Some MVFR vis may develop south of this border, but there is lower confidence in dense fog currently. Once the sun rises, visibilities are expected to improve back to VFR conditions.

Winds are expected to be light and mostly out of the east- southeast today. Clear skies are expected tonight with light, if not calm, winds across the area leading to another chance for fog developing closer to the lake, similar to what is happening this morning. A TEMPO was added for tomorrow morning introducing reduced vis which can be adjusted in later TAF packages with updated confidence in fog development.

Lot Watches

IL...Dense Fog Advisory until 9 AM CDT this morning for ILZ005- ILZ006-ILZ013-ILZ103-ILZ104.

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.