Monthly outlook for O'Fallon, MO: average high 74.9°, average low 52.9°. That is 4.6° above the climate normal for October. Precipitation is expected on 2 days (about 0.9 inches), against a normal of 4 days and 1.7 inches. The warmest day looks like 12 October (90.5°), the coolest 18 October (33.2°).
74.9°/52.9°
Average high / low
+4.6°
Above normal
2 / 4
Wet days / normal
0.9 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
9 October – 18 October
76.1°
67.8°
+4.6°
19 October – 28 October
72.8°
63.6°
+5.1°
29 October – 7 November
at normal
59.5°
—
October records over 66 years
91.9°10 October 1963All-time high
28.8°24 October 1981All-time low
Sat, 1080° / 54°0
80 °
O'Fallon, Saturday, 10 October
Overcast. High 80°, low 54°.
Pressure30.06 inHg
Wind4.6 mph SE
Humidity55%
Visibility6.2 mi
Dew point56°
Sun, 1186° / 52°0
86 °
O'Fallon, Sunday, 11 October
Clear. High 86°, low 52°.
Pressure29.97 inHg
Wind2.3 mph S
Humidity45%
Visibility6.2 mi
Dew point55°
Mon, 1291° / 68°0
91 °
O'Fallon, Monday, 12 October
Clear. High 91°, low 68°.
Pressure29.88 inHg
Wind11.2 mph SW
Humidity38%
Visibility6.2 mi
Dew point58°
Tue, 1390° / 73°0.02
90 °
O'Fallon, Tuesday, 13 October
Light rain. High 90°, low 73°.
Pressure29.88 inHg
Wind8.3 mph W
Humidity55%
Visibility6.2 mi
Dew point69°
Wed, 1478° / 68°0.63
78 °
O'Fallon, Wednesday, 14 October
Rain. High 78°, low 68°.
Pressure30.00 inHg
Wind9 mph NE
Humidity94%
Visibility—
Dew point72°
Thu, 1582° / 63°0.21
82 °
O'Fallon, Thursday, 15 October
Light rain. High 82°, low 63°.
Pressure29.88 inHg
Wind18.2 mph SW
Humidity70%
Visibility—
Dew point66°
Fri, 1664° / 52°0
64 °
O'Fallon, Friday, 16 October
Overcast. High 64°, low 52°.
Pressure30.18 inHg
Wind19.2 mph W
Humidity32%
Visibility—
Dew point31°
Sat, 1749° / 37°0
49 °
O'Fallon, Saturday, 17 October
Partly cloudy. High 49°, low 37°.
Pressure30.45 inHg
Wind18.9 mph NW
Humidity42%
Visibility—
Dew point26°
Sun, 1855° / 33°0
55 °
O'Fallon, Sunday, 18 October
Partly cloudy. High 55°, low 33°.
Pressure30.47 inHg
Wind4.9 mph N
Humidity34%
Visibility—
Dew point22°
Mon, 1962° / 42°0
62 °
O'Fallon, Monday, 19 October
Overcast. High 62°, low 42°.
Pressure30.39 inHg
Wind7.8 mph S
Humidity32%
Visibility—
Dew point28°
Tue, 2068° / 45°0
68 °
O'Fallon, Tuesday, 20 October
Clear. High 68°, low 45°.
Pressure30.39 inHg
Wind6 mph SE
Humidity29%
Visibility—
Dew point30°
Wed, 2173° / 47°0
73 °
O'Fallon, Wednesday, 21 October
Clear. High 73°, low 47°.
Pressure30.30 inHg
Wind7.4 mph S
Humidity29%
Visibility—
Dew point34°
Thu, 2276° / 50°0
76 °
O'Fallon, Thursday, 22 October
Clear. High 76°, low 50°.
Pressure30.15 inHg
Wind7.5 mph SW
Humidity30%
Visibility—
Dew point38°
Fri, 2378° / 52°0
78 °
O'Fallon, Friday, 23 October
Clear. High 78°, low 52°.
Pressure30.03 inHg
Wind8 mph S
Humidity30%
Visibility—
Dew point39°
Sat, 2480° / 55°0
80 °
O'Fallon, Saturday, 24 October
Overcast. High 80°, low 55°.
Pressure30.03 inHg
Wind10.2 mph SW
Humidity24%
Visibility—
Dew point35°
From day 17 onward the outlook is built from 60-year climate statistics
Sun, 2562° / 47°0.13
62 °
O'Fallon, Sunday, 25 October
Climate normal for this date — 60-year average.
Average high62°
Average low47°
Average precipitation0.13 in
Chance of precipitation30%
Record high82° (2023)
Record low31° (2013)
Mon, 2661° / 46°0.13
61 °
O'Fallon, Monday, 26 October
Climate normal for this date — 60-year average.
Average high61°
Average low46°
Average precipitation0.13 in
Chance of precipitation35%
Record high83° (1963)
Record low30° (1962)
Tue, 2762° / 46°0.09
62 °
O'Fallon, Tuesday, 27 October
Climate normal for this date — 60-year average.
Average high62°
Average low46°
Average precipitation0.09 in
Chance of precipitation20%
Record high80° (2023)
Record low33° (2001)
Wed, 2861° / 46°0.05
61 °
O'Fallon, Wednesday, 28 October
Climate normal for this date — 60-year average.
Average high61°
Average low46°
Average precipitation0.05 in
Chance of precipitation23%
Record high78° (1999)
Record low31° (1969)
Thu, 2962° / 46°0.13
62 °
O'Fallon, Thursday, 29 October
Climate normal for this date — 60-year average.
Average high62°
Average low46°
Average precipitation0.13 in
Chance of precipitation28%
Record high82° (2024)
Record low30° (2017)
Fri, 3063° / 47°0.12
63 °
O'Fallon, Friday, 30 October
Climate normal for this date — 60-year average.
Average high63°
Average low47°
Average precipitation0.12 in
Chance of precipitation30%
Record high82° (2024)
Record low29° (1980)
Sat, 3162° / 47°0.16
62 °
O'Fallon, Saturday, 31 October
Climate normal for this date — 60-year average.
Average high62°
Average low47°
Average precipitation0.16 in
Chance of precipitation42%
Record high80° (1968)
Record low29° (1993)
Sun, 0161° / 46°0.19
61 °
O'Fallon, Sunday, 1 November
Climate normal for this date — 60-year average.
Average high61°
Average low46°
Average precipitation0.19 in
Chance of precipitation28%
Record high80° (2016)
Record low26° (2023)
Mon, 0260° / 44°0.09
60 °
O'Fallon, Monday, 2 November
Climate normal for this date — 60-year average.
Average high60°
Average low44°
Average precipitation0.09 in
Chance of precipitation35%
Record high80° (2016)
Record low27° (1966)
Tue, 0358° / 43°0.12
58 °
O'Fallon, Tuesday, 3 November
Climate normal for this date — 60-year average.
Average high58°
Average low43°
Average precipitation0.12 in
Chance of precipitation30%
Record high78° (1987)
Record low19° (1991)
Wed, 0458° / 44°0.15
58 °
O'Fallon, Wednesday, 4 November
Climate normal for this date — 60-year average.
Average high58°
Average low44°
Average precipitation0.15 in
Chance of precipitation28%
Record high78° (1978)
Record low19° (1991)
Thu, 0557° / 43°0.17
57 °
O'Fallon, Thursday, 5 November
Climate normal for this date — 60-year average.
Average high57°
Average low43°
Average precipitation0.17 in
Chance of precipitation35%
Record high78° (1978)
Record low24° (1991)
Fri, 0657° / 42°0.09
57 °
O'Fallon, Friday, 6 November
Climate normal for this date — 60-year average.
Average high57°
Average low42°
Average precipitation0.09 in
Chance of precipitation32%
Record high77° (2023)
Record low28° (1982)
Sat, 0758° / 42°0.07
58 °
O'Fallon, Saturday, 7 November
Climate normal for this date — 60-year average.
Average high58°
Average low42°
Average precipitation0.07 in
Chance of precipitation13%
Record high74° (1980)
Record low15° (1991)
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 O'Fallon, MO 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 O'Fallon, MO 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.