40.7180, -87.8600

1. Sat10 PM56°5 mph
2. 11 PM55°3 mph
3. Sun12 AM54°3 mph
4. 1 AM52°2 mph
5. 2 AM51°2 mph
6. 3 AM50°2 mph
7. 4 AM50°1%2 mph
8. 5 AM49°2%2 mph
9. 6 AM48°2%2 mph
10. 7 AM48°1%2 mph
11. 8 AM51°2 mph
12. 9 AM57°2 mph
13. 10 AM62°2 mph
14. 11 AM66°3 mph
15. 12 PM68°5 mph
16. 1 PM70°5 mph
17. 2 PM72°6 mph
18. 3 PM72°7 mph
19. 4 PM72°7 mph
20. 5 PM70°7 mph
21. 6 PM67°6 mph
22. 7 PM62°6 mph
23. 8 PM59°6 mph
24. 9 PM56°6 mph
25. 10 PM54°5 mph
26. 11 PM53°5 mph
27. Mon12 AM52°5 mph
28. 1 AM51°3 mph
29. 2 AM50°3 mph
30. 3 AM50°3 mph
31. 4 AM49°3 mph
32. 5 AM49°3 mph
33. 6 AM48°2 mph
34. 7 AM49°2 mph
35. 8 AM53°2 mph
36. 9 AM58°2 mph
37. 10 AM64°2 mph
38. 11 AM68°2 mph
39. 12 PM71°2 mph
40. 1 PM74°2 mph
41. 2 PM75°2 mph
42. 3 PM76°2 mph
43. 4 PM75°2 mph
44. 5 PM74°2 mph
45. 6 PM71°2 mph
46. 7 PM68°2 mph
47. 8 PM65°3 mph
48. 9 PM62°3 mph

Scroll sideways for more hours. Pick an hour for every number.

1. TodaySep 2674°48°Partly Cloudy then Patchy Fog0%wind 6 mph
2. SunSep 2772°48°Patchy Fog then Mostly Sunny2%wind 7 mph
3. MonSep 2876°52°Mostly Sunny0%wind 5 mph
4. TueSep 2977°62°Mostly Sunny15%wind 5 mph
5. WedSep 3075°63°Chance Showers And Thunderstorms49%wind 6 mph · gusts 13 mph
6. ThuOct 174°60°Showers And Thunderstorms Likely67%wind 7 mph · gusts 14 mph
7. FriOct 270°56°Chance Showers And Thunderstorms55%wind 6 mph · gusts 12 mph
8. SatOct 370°55°Chance Showers And Thunderstorms29%wind 6 mph · gusts 12 mph
9. SunOct 467°51°National Blend21%0.12 inwind 6 mph · gusts 12 mph
10. MonOct 565°49°National Blend9%wind 5 mph · gusts 10 mph
11. TueOct 667°52°National Blend12%0.02 inwind 5 mph
12. WedOct 7~69°48°Model mean
13. ThuOct 8~67°51°Model mean
14. FriOct 9~66°45°Model mean
15. SatOct 10~67°49°Model mean0.03 in
16. SunOct 11~64°46°Model mean

• Feels like56°
• WindE 5 mph
• Radar over this pointno reading
• Humidity70%
• Dew point47°
• Pressure—
• UV index—
• Air quality—
• Visibility—
• Sunrise and sunsetSunrise · Sunset · set
• Moonrise6:31 PMMoonset 6:37 AM
• Moon phaseFull moon100% lit

NOAA’s weighted blend of every model it runs, to eleven days, with the chances the grid above does not carry. Where the local office’s grid reaches, its figure sits beneath the blend’s; where it does not, the blend stands alone.

1. TodaySep 26—46°NWS grid 74° / 48°rain 0%wind 2 mph
2. SunSep 2773°49°NWS grid 72° / 48°rain 0%wind 3 mph
3. MonSep 2876°52°NWS grid 76° / 52°rain 0%wind 2 mph
4. TueSep 2977°62°NWS grid 77° / 62°rain 21%wind 5 mph
5. WedSep 3076°64°NWS grid 75° / 63°rain 51%thunder 21%0.07 inwind 6 mph · gusts 13 mph
6. ThuOct 175°59°NWS grid 74° / 60°rain 67%thunder 17%0.78 inwind 6 mph · gusts 13 mph
7. FriOct 269°56°NWS grid 70° / 56°rain 48%thunder 14%0.88 inwind 5 mph · gusts 12 mph
8. SatOct 368°54°NWS grid 70° / 55°rain 34%thunder 18%0.46 inwind 5 mph · gusts 10 mph
9. SunOct 467°51°Beyond the NWS gridrain 21%thunder 10%0.12 inwind 6 mph · gusts 12 mph
10. MonOct 565°49°Beyond the NWS gridrain 9%wind 5 mph · gusts 10 mph
11. TueOct 667°52°Beyond the NWS gridrain 12%0.02 inwind 5 mph
12. WedOct 768°—Beyond the NWS gridrain 10%wind 6 mph

Each line is one model’s own forecast at its own grid cell: three kilometers for HRRR, a quarter of a degree for the global models, which can sit a few hundred meters above or below the town. Where they agree the forecast is settled; where they part is where it is not.

NWS gridBlendHRRRGFSGEFS ± spreadECMWFECMWF AI

A ~ marks a high or low read from six-hourly steps, which miss the true extreme by a degree or two.

ECMWF ensemble meteogram

10 daysTemperature plume

No forecast has skill day by day past about two weeks, and this page does not print one. Where the models stop, the calendar takes over: the 1991 to 2020 normal for each date, the record high and low ever set on it, and where the Climate Prediction Center leans warm, cool, wet or dry over the coming weeks, the month and the season. A site that shows a high for a date three months out is showing you this normal with a wobble.

The forecast reaches Sun Oct 11, from the NWS grid, then the National Blend, then the mean of the global models. Beyond it the lines are the calendar.

Forecast high and lowNormal high and lowRecord high and lowCPC leans warmer than normalCPC near normal or equal chances

None of these is a measurement. Each is a rating of the forecast ahead, and of what is happening at the point right now, against what the activity or the ailment is known to mind, and each names the figure that decided it. An ailment or a pest is rated as a risk, low to extreme; an activity, a chore or a journey as a condition, poor to ideal.

The sun is down, so each rating says which span it is for: tomorrow’s daylight, tonight, or the next 24 hours.

Tonight has no dark, clear hour without a bright moon in this forecast. Rated poor.

Dark is the sun 18 degrees below the horizon; where it never gets that low, 12 degrees, marked nautical. Clear is sky cover of 20% or less. A bright moon is one above the horizon with a quarter or more of its disc lit. Transparency in the table is estimated from surface humidity (70% and 85% mark fair and poor) and visibility, since the forecast carries no haze or high cloud moisture. Seeing and transparency by hour, where shown, are Environment and Climate Change Canada’s astronomy forecast (regional model; seeing from cloud, wind shear, turbulence near the ground and the surface temperature trend; transparency from the moisture through the whole air column), under the Open Government Licence - Canada. Dew is the air within 2 °C of its dew point. Excellent is four or more clear moonless hours with good transparency; good is three; fair is one, or two clear hours.

Golden hour is the sun between 6 degrees above the horizon and 4 degrees below it; blue hour is the sun between 4 and 6 degrees below. These are the definitions timeanddate.com and PhotoPills use. Directions are degrees clockwise from true north, where the sun’s upper edge and the moon’s center cross a flat horizon; hills and buildings change both. None means the sun does not reach that height on the day; all day means it stays inside the band.

This hour: fly with caution (wind at 400 ft near or over your limit, gusts near or over your limit, night: lighting and night training required (107.29)). Next good stretch: Sun 7 AM to 6 PM, 11 hours.

Today: civil twilight for Part 107 6:13 AM to sunrise 6:43 AM, and sunset 6:42 PM to 7:12 PM. Anti-collision lighting is required in those minutes and at night.

Good Caution No-fly

Flight restrictions nearby

Reading the FAA’s temporary flight restrictions.

Flight restrictions on the map. TFRs are not the whole picture: controlled airspace around airports needs LAANC authorization. Check the FAA’s B4UFLY.

Wind at 400 ft is estimated from the 10 m forecast by the power law, with exponents for each Pasquill stability class (Irwin 1979, rural, as in EPA dispersion models; the class from wind, sun height and cloud, after Turner 1970); gusts keep the ground gust’s margin. Caution from three quarters of your limit; the default 24 mph is the wind resistance printed for common sub-250 g drones. 14 CFR 107.51: “The minimum flight visibility, as observed from the location of the control station must be no less than 3 statute miles” and at least “500 feet below the cloud”. 14 CFR 107.29: “No person may operate a small unmanned aircraft system during periods of civil twilight unless the small unmanned aircraft has lighted anti-collision lighting visible for at least 3 statute miles”; civil twilight is the 30 minutes before sunrise and after sunset, in Alaska the Air Almanac’s. Kp: SWPC’s scales say satellite navigation problems may occur at G3 (Kp 7) and navigation is “degraded for hours” at G4 (Kp 8); Kp 5 is the typical app warning. Typical limits, not rules: rain chance 30% caution and 60% no-fly, thunder 10% and 20%, below 0 °C caution and −10 °C no-fly, over 40 °C caution. Your drone’s manual and the airspace come first.

Hours fit for spraying, and the days dry enough for fieldwork and hay, read from this forecast’s wind, gusts, humidity, temperature and rain.

Spraying windows

• Sat 10 PM to Sun 1 AM 3 hours, every hour within the rules
• Sun 11 AM to 11 PM 12 hours, every hour within the rules
• Mon 8 PM to 10 PM 2 hours, every hour within the rules
• Tue 9 AM to Wed 3 AM 18 hours, every hour within the rules
• Sat 10 AM to 4 PM 6 hours, every hour within the rules

Good Marginal No

Field days

Spraying: sustained wind 3 to 10 mph, the range US extension services and most labels give; gusts no more than 15 mph (this page’s limit); delta T (air minus wet-bulb temperature) 2 to 8 °C preferred and 8 to 10 °C marginal, from GRDC guidance, with the wet bulb by Stull’s formula; no hour at a 30% chance of rain or 0.25 mm forecast during the rain-free time. Follow the product label, which overrides all of this. Field days: dry is no daytime hour at a 30% chance and under 1 mm all day, wet is 6 mm (0.25 in) or more; soil moisture is not in the forecast, so ground still wet from earlier rain is not accounted for. Hay drying marks a dry day with humidity down to 50% and a breeze of 5 mph or more.

The best-rated day this week is Saturday, rated best.

Periods in bold fall within an hour of sunrise or sunset. The weather’s side is the fishing index

Major periods are two hours centered on the moon’s passage overhead and underfoot; minor periods are one hour centered on moonrise and moonset: the conventional durations of John Alden Knight’s solunar tables (1936). The rating is this site’s: one point to start, two more within a day and a half of a new or full moon (one more within three and a half days), and one more when a period falls within an hour of sunrise or sunset. The theory has mixed support in fisheries research; the times are exact astronomy.

1. Tonight48° · 2% · ENE 0–5 mph

   Patchy fog after 2am. Partly cloudy, with a low around 48. East northeast wind 0 to 5 mph.

2. Sunday72° · 2% · NE 0–5 mph

   Patchy fog before 9am. Mostly sunny. High near 72, with temperatures falling to around 70 in the afternoon. Northeast wind 0 to 5 mph.

3. Sunday Night48° · N 5 mph

   Partly cloudy, with a low around 48. North wind around 5 mph.

4. Monday76° · 0 mph

   Mostly sunny, with a high near 76. North wind around 0 mph.

5. Monday Night52° · E 0–5 mph

   Mostly clear, with a low around 52. East wind 0 to 5 mph.

6. Tuesday77° · SSE 0–5 mph

   Mostly sunny, with a high near 77.

7. Tuesday Night62° · 26% · S 5 mph

   A chance of rain showers after 7pm. Mostly cloudy, with a low around 62.

8. Wednesday75° · 49% · S 5 mph

   A chance of rain showers before 7am, then a chance of showers and thunderstorms. Mostly cloudy, with a high near 75.

9. Wednesday Night63° · 50% · S 0–5 mph

   A chance of rain showers before 1am, then a chance of showers and thunderstorms. Mostly cloudy, with a low around 63.

10. Thursday74° · 67% · SSW 5 mph

    Showers and thunderstorms likely. Mostly cloudy, with a high near 74.

11. Thursday Night60° · 67% · W 5 mph

    Showers and thunderstorms likely. Mostly cloudy, with a low around 60.

12. Friday70° · 44% · N 5 mph

    A chance of showers and thunderstorms. Partly sunny, with a high near 70.

13. Friday Night56° · 39% · NE 0–5 mph

    A chance of showers and thunderstorms. Mostly cloudy, with a low around 56.

14. Saturday70° · 29% · ESE 0–5 mph

    A chance of showers and thunderstorms. Mostly sunny, with a high near 70.

Written by the forecaster on duty for their own colleagues and for anyone who wants to know why the forecast says what it says. It is not edited for the public, so it uses the office’s shorthand; it is also the most honest thing any weather service publishes.

FLUS43 KLOT 261948
HWOLOT

Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
248 PM CDT Sat Sep 26 2026

ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-272000-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
248 PM CDT Sat Sep 26 2026 /348 PM EDT Sat Sep 26 2026/

This Hazardous Weather Outlook is for portions of north central
Illinois...northeast Illinois and northwest Indiana.

.DAY ONE...Tonight.

  No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Tuesday through Friday...
  Limited Thunderstorm Risk at times.

.SPOTTER INFORMATION STATEMENT...

  Spotter activation will not be necessary through tonight.

$$

LMZ740>745-272000-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
248 PM CDT Sat Sep 26 2026

This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.

.DAY ONE...Tonight.

  No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Thursday...
  Limited Thunderstorm Risk.
Friday...
  Hazardous conditions for small craft are possible.
  Limited Thunderstorm Risk.

$$

Yack

Visit us at www.weather.gov/chicago

The national centers each publish a judgment the local grid does not carry. Read here at this exact coordinate.

The last spring freeze (32°F) usually comes around April 24 and the first fall freeze around October 16: a growing season of about 174 days.

One fall in ten brings a freeze by October 1; one spring in ten still has one after May 10.

Climate of 40.72, -87.86: normals, records and every month

The forecast office edits about sixty fields for every cell of its grid. The common ones are above; these are the rest, as the daily extreme, for anyone who needs the mixing height, the fire danger or the swell.

Each forecast day against the same calendar date at the nearest long-record station: the 1991 to 2020 normal, and the record high and low with the year they were set.