Monthly outlook for Winnetka, IL: average high 78°, average low 67°. That is 0.4° below the climate normal for August. Precipitation is expected on 7 days (about 2.5 inches), against a normal of 6 days and 1.8 inches. The warmest day looks like 19 August (83.9°), the coolest 23 August (58.7°).
78°/67°
Average high / low
−0.4°
Below normal
7 / 6
Wet days / normal
2.5 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
8 August – 17 August
79.9°
78.9°
+0.6°
18 August – 27 August
74.8°
78.6°
-2.1°
28 August – 6 September
at normal
77.2°
—
August records over 66 years
99.7°24 August 2023All-time high
52.3°22 August 2024All-time low
Climate normals and records are computed from the nearest reference point — Evanston (5 mi).
Sun, 0983° / 66°1.27
83 °
Winnetka, Sunday, 9 August
Heavy rain. High 83°, low 66°.
Pressure29.94 inHg
Wind3.7 mph N
Humidity92%
Visibility2.4 mi
Dew point64°
Mon, 1084° / 73°0.19
84 °
Winnetka, Monday, 10 August
Heavy rain. High 84°, low 73°.
Pressure29.88 inHg
Wind4.4 mph S
Humidity84%
Visibility6.2 mi
Dew point69°
Tue, 1181° / 72°0.37
81 °
Winnetka, Tuesday, 11 August
Rain. High 81°, low 72°.
Pressure29.80 inHg
Wind7.5 mph N
Humidity73%
Visibility6.2 mi
Dew point71°
Wed, 1284° / 69°0.02
84 °
Winnetka, Wednesday, 12 August
Light rain. High 84°, low 69°.
Pressure29.85 inHg
Wind1.6 mph E
Humidity61%
Visibility6.2 mi
Dew point64°
Thu, 1373° / 66°0.07
73 °
Winnetka, Thursday, 13 August
Light rain. High 73°, low 66°.
Pressure29.97 inHg
Wind12.7 mph NE
Humidity66%
Visibility—
Dew point59°
Fri, 1472° / 65°0
72 °
Winnetka, Friday, 14 August
Clear. High 72°, low 65°.
Pressure30.18 inHg
Wind11.2 mph NE
Humidity50%
Visibility—
Dew point52°
Sat, 1577° / 62°0
77 °
Winnetka, Saturday, 15 August
Overcast. High 77°, low 62°.
Pressure30.30 inHg
Wind7.8 mph E
Humidity40%
Visibility—
Dew point48°
Sun, 1681° / 63°0
81 °
Winnetka, Sunday, 16 August
Partly cloudy. High 81°, low 63°.
Pressure30.18 inHg
Wind9.8 mph SW
Humidity41%
Visibility—
Dew point52°
Mon, 1781° / 69°0.04
81 °
Winnetka, Monday, 17 August
Light rain. High 81°, low 69°.
Pressure30.00 inHg
Wind7 mph S
Humidity84%
Visibility—
Dew point65°
Tue, 1878° / 71°0.01
78 °
Winnetka, Tuesday, 18 August
Light rain. High 78°, low 71°.
Pressure30.03 inHg
Wind8.9 mph NE
Humidity66%
Visibility—
Dew point65°
Wed, 1984° / 69°0.43
84 °
Winnetka, Wednesday, 19 August
Rain. High 84°, low 69°.
Pressure29.91 inHg
Wind5.6 mph S
Humidity53%
Visibility—
Dew point63°
Thu, 2075° / 69°0.01
75 °
Winnetka, Thursday, 20 August
Light rain. High 75°, low 69°.
Pressure29.91 inHg
Wind11.1 mph NE
Humidity75%
Visibility—
Dew point65°
Fri, 2174° / 67°0
74 °
Winnetka, Friday, 21 August
Partly cloudy. High 74°, low 67°.
Pressure30.00 inHg
Wind10.6 mph NE
Humidity65%
Visibility—
Dew point60°
Sat, 2275° / 62°0.06
75 °
Winnetka, Saturday, 22 August
Light rain. High 75°, low 62°.
Pressure29.97 inHg
Wind18.9 mph NE
Humidity80%
Visibility—
Dew point59°
Sun, 2364° / 59°0
64 °
Winnetka, Sunday, 23 August
Clear. High 64°, low 59°.
Pressure30.27 inHg
Wind16.5 mph NE
Humidity53%
Visibility—
Dew point46°
From day 17 onward the outlook is built from 60-year climate statistics
Mon, 2479° / 68°0.12
79 °
Winnetka, Monday, 24 August
Climate normal for this date — 60-year average.
Average high79°
Average low68°
Average precipitation0.12 in
Chance of precipitation30%
Record high100° (2023)
Record low58° (1966)
Tue, 2579° / 68°0.07
79 °
Winnetka, Tuesday, 25 August
Climate normal for this date — 60-year average.
Average high79°
Average low68°
Average precipitation0.07 in
Chance of precipitation23%
Record high92° (2024)
Record low56° (2017)
Wed, 2680° / 68°0.15
80 °
Winnetka, Wednesday, 26 August
Climate normal for this date — 60-year average.
Average high80°
Average low68°
Average precipitation0.15 in
Chance of precipitation33%
Record high96° (2024)
Record low55° (2025)
Thu, 2779° / 69°0.11
79 °
Winnetka, Thursday, 27 August
Climate normal for this date — 60-year average.
Average high79°
Average low69°
Average precipitation0.11 in
Chance of precipitation32%
Record high97° (2024)
Record low57° (2025)
Fri, 2879° / 68°0.12
79 °
Winnetka, Friday, 28 August
Climate normal for this date — 60-year average.
Average high79°
Average low68°
Average precipitation0.12 in
Chance of precipitation33%
Record high92° (2021)
Record low53° (1986)
Sat, 2979° / 68°0.11
79 °
Winnetka, Saturday, 29 August
Climate normal for this date — 60-year average.
Average high79°
Average low68°
Average precipitation0.11 in
Chance of precipitation30%
Record high91° (1984)
Record low53° (1965)
Sun, 3078° / 67°0.13
78 °
Winnetka, Sunday, 30 August
Climate normal for this date — 60-year average.
Average high78°
Average low67°
Average precipitation0.13 in
Chance of precipitation27%
Record high91° (2013)
Record low57° (1965)
Mon, 3177° / 66°0.07
77 °
Winnetka, Monday, 31 August
Climate normal for this date — 60-year average.
Average high77°
Average low66°
Average precipitation0.07 in
Chance of precipitation22%
Record high89° (2012)
Record low58° (2025)
Tue, 0177° / 67°0.12
77 °
Winnetka, Tuesday, 1 September
Climate normal for this date — 60-year average.
Average high77°
Average low67°
Average precipitation0.12 in
Chance of precipitation32%
Record high90° (2011)
Record low56° (1987)
Wed, 0278° / 67°0.05
78 °
Winnetka, Wednesday, 2 September
Climate normal for this date — 60-year average.
Average high78°
Average low67°
Average precipitation0.05 in
Chance of precipitation25%
Record high89° (2023)
Record low53° (2017)
Thu, 0377° / 66°0.08
77 °
Winnetka, Thursday, 3 September
Climate normal for this date — 60-year average.
Average high77°
Average low66°
Average precipitation0.08 in
Chance of precipitation28%
Record high94° (2023)
Record low54° (1974)
Fri, 0476° / 66°0.08
76 °
Winnetka, Friday, 4 September
Climate normal for this date — 60-year average.
Average high76°
Average low66°
Average precipitation0.08 in
Chance of precipitation30%
Record high92° (2023)
Record low50° (2025)
Sat, 0576° / 65°0.08
76 °
Winnetka, Saturday, 5 September
Climate normal for this date — 60-year average.
Average high76°
Average low65°
Average precipitation0.08 in
Chance of precipitation22%
Record high91° (2023)
Record low55° (2017)
Sun, 0676° / 65°0.1
76 °
Winnetka, Sunday, 6 September
Climate normal for this date — 60-year average.
Average high76°
Average low65°
Average precipitation0.1 in
Chance of precipitation35%
Record high90° (1990)
Record low50° (2025)
About the monthly outlook
How accurate is a 30-day forecast?
The first 16 days come from weather models — reliable for the first 3–5 days and progressively less so after that. Days 17 through 30 for Winnetka, IL are built from the climate normal, the 60-year average, so they show typical weather for those dates rather than a specific forecast.
What does "above normal" mean?
We compare the forecast against the climate normal for those exact calendar days, computed from 60 years of observations. The deviation shows how much the coming month differs from a typical one.
Where do the 66-year records come from?
They are real temperature extremes recorded in Winnetka, IL since 1960: the highest and lowest reading for each calendar date, with the year it happened.
How often is it updated?
The forecast portion refreshes every hour; the climate portion is based on long-term data and stays stable.