Monthly outlook for Ontarioville, IL: average high 78°, average low 62.3°. That is 1° below the climate normal for August. Precipitation is expected on 3 days (about 1.7 inches), against a normal of 6 days and 1.8 inches. The warmest day looks like 9 August (87.2°), the coolest 20 August (53.7°).
78°/62.3°
Average high / low
−1°
Below normal
3 / 6
Wet days / normal
1.7 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
9 August – 18 August
80.1°
79.9°
+0.1°
19 August – 28 August
74.5°
79.9°
-3°
29 August – 7 September
at normal
78.1°
—
August records over 66 years
99.3°24 August 2023All-time high
45.1°29 August 1965All-time low
Climate normals and records are computed from the nearest reference point — Glendale Heights (6 mi).
Mon, 1087° / 71°0.65
87 °
Ontarioville, Monday, 10 August
Heavy rain. High 87°, low 71°.
Pressure29.91 inHg
Wind5.2 mph E
Humidity70%
Visibility6.2 mi
Dew point71°
Tue, 1184° / 69°0.19
84 °
Ontarioville, Tuesday, 11 August
Rain. High 84°, low 69°.
Pressure29.80 inHg
Wind7.1 mph SW
Humidity87%
Visibility6.2 mi
Dew point73°
Wed, 1280° / 66°0.01
80 °
Ontarioville, Wednesday, 12 August
Light rain. High 80°, low 66°.
Pressure29.88 inHg
Wind6.6 mph NW
Humidity69%
Visibility6.2 mi
Dew point67°
Thu, 1374° / 62°0
74 °
Ontarioville, Thursday, 13 August
Overcast. High 74°, low 62°.
Pressure30.03 inHg
Wind8.7 mph NE
Humidity53%
Visibility—
Dew point54°
Fri, 1478° / 60°0
78 °
Ontarioville, Friday, 14 August
Clear. High 78°, low 60°.
Pressure30.12 inHg
Wind7.5 mph N
Humidity45%
Visibility—
Dew point52°
Sat, 1573° / 62°0
73 °
Ontarioville, Saturday, 15 August
Overcast. High 73°, low 62°.
Pressure30.27 inHg
Wind11.7 mph SW
Humidity51%
Visibility—
Dew point53°
Sun, 1677° / 62°0
77 °
Ontarioville, Sunday, 16 August
Overcast. High 77°, low 62°.
Pressure30.15 inHg
Wind4.6 mph SW
Humidity57%
Visibility—
Dew point56°
Mon, 1779° / 64°0.01
79 °
Ontarioville, Monday, 17 August
Light rain. High 79°, low 64°.
Pressure30.06 inHg
Wind6.9 mph W
Humidity63%
Visibility—
Dew point62°
Tue, 1881° / 66°0
81 °
Ontarioville, Tuesday, 18 August
Overcast. High 81°, low 66°.
Pressure29.97 inHg
Wind11.8 mph SW
Humidity64%
Visibility—
Dew point65°
Wed, 1974° / 60°0.02
74 °
Ontarioville, Wednesday, 19 August
Light rain. High 74°, low 60°.
Pressure29.94 inHg
Wind15.8 mph NW
Humidity76%
Visibility—
Dew point58°
Thu, 2068° / 54°0
68 °
Ontarioville, Thursday, 20 August
Overcast. High 68°, low 54°.
Pressure30.06 inHg
Wind11.1 mph N
Humidity68%
Visibility—
Dew point51°
Fri, 2175° / 54°0
75 °
Ontarioville, Friday, 21 August
Clear. High 75°, low 54°.
Pressure30.06 inHg
Wind10.3 mph NE
Humidity48%
Visibility—
Dew point51°
Sat, 2269° / 58°0.01
69 °
Ontarioville, Saturday, 22 August
Light rain. High 69°, low 58°.
Pressure29.91 inHg
Wind10.3 mph S
Humidity82%
Visibility—
Dew point56°
Sun, 2380° / 64°0
80 °
Ontarioville, Sunday, 23 August
Clear. High 80°, low 64°.
Pressure29.91 inHg
Wind13 mph W
Humidity46%
Visibility—
Dew point55°
Mon, 2482° / 61°0
82 °
Ontarioville, Monday, 24 August
Overcast. High 82°, low 61°.
Pressure30.00 inHg
Wind5.9 mph SW
Humidity48%
Visibility—
Dew point58°
From day 17 onward the outlook is built from 60-year climate statistics
Tue, 2580° / 64°0.07
80 °
Ontarioville, Tuesday, 25 August
Climate normal for this date — 60-year average.
Average high80°
Average low64°
Average precipitation0.07 in
Chance of precipitation25%
Record high92° (2003)
Record low52° (2017)
Wed, 2681° / 65°0.15
81 °
Ontarioville, Wednesday, 26 August
Climate normal for this date — 60-year average.
Average high81°
Average low65°
Average precipitation0.15 in
Chance of precipitation32%
Record high95° (2024)
Record low51° (1964)
Thu, 2780° / 66°0.11
80 °
Ontarioville, Thursday, 27 August
Climate normal for this date — 60-year average.
Average high80°
Average low66°
Average precipitation0.11 in
Chance of precipitation30%
Record high97° (2024)
Record low54° (2015)
Fri, 2880° / 65°0.13
80 °
Ontarioville, Friday, 28 August
Climate normal for this date — 60-year average.
Average high80°
Average low65°
Average precipitation0.13 in
Chance of precipitation37%
Record high93° (1984)
Record low48° (1986)
Sat, 2980° / 64°0.11
80 °
Ontarioville, Saturday, 29 August
Climate normal for this date — 60-year average.
Average high80°
Average low64°
Average precipitation0.11 in
Chance of precipitation30%
Record high94° (1984)
Record low45° (1965)
Sun, 3079° / 63°0.13
79 °
Ontarioville, Sunday, 30 August
Climate normal for this date — 60-year average.
Average high79°
Average low63°
Average precipitation0.13 in
Chance of precipitation28%
Record high93° (2013)
Record low51° (1986)
Mon, 3178° / 63°0.08
78 °
Ontarioville, Monday, 31 August
Climate normal for this date — 60-year average.
Average high78°
Average low63°
Average precipitation0.08 in
Chance of precipitation18%
Record high90° (2012)
Record low51° (2009)
Tue, 0178° / 63°0.12
78 °
Ontarioville, Tuesday, 1 September
Climate normal for this date — 60-year average.
Average high78°
Average low63°
Average precipitation0.12 in
Chance of precipitation32%
Record high93° (2011)
Record low47° (2009)
Wed, 0279° / 63°0.04
79 °
Ontarioville, Wednesday, 2 September
Climate normal for this date — 60-year average.
Average high79°
Average low63°
Average precipitation0.04 in
Chance of precipitation22%
Record high92° (2008)
Record low48° (1965)
Thu, 0378° / 63°0.09
78 °
Ontarioville, Thursday, 3 September
Climate normal for this date — 60-year average.
Average high78°
Average low63°
Average precipitation0.09 in
Chance of precipitation30%
Record high94° (2023)
Record low48° (1974)
Fri, 0477° / 62°0.09
77 °
Ontarioville, Friday, 4 September
Climate normal for this date — 60-year average.
Average high77°
Average low62°
Average precipitation0.09 in
Chance of precipitation32%
Record high92° (2023)
Record low47° (1974)
Sat, 0577° / 61°0.08
77 °
Ontarioville, Saturday, 5 September
Climate normal for this date — 60-year average.
Average high77°
Average low61°
Average precipitation0.08 in
Chance of precipitation23%
Record high90° (2023)
Record low50° (2010)
Sun, 0677° / 61°0.11
77 °
Ontarioville, Sunday, 6 September
Climate normal for this date — 60-year average.
Average high77°
Average low61°
Average precipitation0.11 in
Chance of precipitation37%
Record high91° (1990)
Record low47° (1988)
Mon, 0777° / 61°0.09
77 °
Ontarioville, Monday, 7 September
Climate normal for this date — 60-year average.
Average high77°
Average low61°
Average precipitation0.09 in
Chance of precipitation27%
Record high91° (1960)
Record low47° (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 Ontarioville, 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 Ontarioville, 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.