Monthly outlook for Alton, IL: average high 74.2°, average low 54.5°. That is 4.8° above the climate normal for October. Precipitation is expected on 4 days (about 0.6 inches), against a normal of 5 days and 2.0 inches. The warmest day looks like 12 October (90.2°), the coolest 18 October (34.6°).
74.2°/54.5°
Average high / low
+4.8°
Above normal
4 / 5
Wet days / normal
0.6 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
11 October – 20 October
73.2°
66.6°
+3.6°
21 October – 30 October
75.8°
63°
+7.1°
31 October – 9 November
at normal
58.6°
—
October records over 66 years
91.4°1 October 2019All-time high
28.6°24 October 1981All-time low
Climate normals and records are computed from the nearest reference point — Edwardsville (12 mi).
Mon, 1290° / 60°0
90 °
Alton, Monday, 12 October
Clear. High 90°, low 60°.
Pressure29.91 inHg
Wind9.8 mph SW
Humidity48%
Visibility6.2 mi
Dew point61°
Tue, 1389° / 69°0
89 °
Alton, Tuesday, 13 October
Clear. High 89°, low 69°.
Pressure29.91 inHg
Wind8.9 mph SW
Humidity56%
Visibility6.2 mi
Dew point67°
Wed, 1478° / 70°0.18
78 °
Alton, Wednesday, 14 October
Rain. High 78°, low 70°.
Pressure30.03 inHg
Wind7.8 mph SW
Humidity87%
Visibility3.4 mi
Dew point71°
Thu, 1576° / 69°0.24
76 °
Alton, Thursday, 15 October
Light rain. High 76°, low 69°.
Pressure30.03 inHg
Wind6.5 mph SW
Humidity93%
Visibility6.2 mi
Dew point73°
Fri, 1671° / 54°0.04
71 °
Alton, Friday, 16 October
Light rain. High 71°, low 54°.
Pressure30.36 inHg
Wind16.9 mph N
Humidity46%
Visibility—
Dew point40°
Sat, 1749° / 37°0
49 °
Alton, Saturday, 17 October
Clear. High 49°, low 37°.
Pressure30.59 inHg
Wind12.3 mph N
Humidity19%
Visibility—
Dew point6°
Sun, 1858° / 35°0
58 °
Alton, Sunday, 18 October
Clear. High 58°, low 35°.
Pressure30.53 inHg
Wind13.1 mph S
Humidity18%
Visibility—
Dew point9°
Mon, 1968° / 42°0
68 °
Alton, Monday, 19 October
Clear. High 68°, low 42°.
Pressure30.42 inHg
Wind11.5 mph SW
Humidity17%
Visibility—
Dew point16°
Tue, 2069° / 47°0
69 °
Alton, Tuesday, 20 October
Overcast. High 69°, low 47°.
Pressure30.33 inHg
Wind9.6 mph S
Humidity22%
Visibility—
Dew point25°
Wed, 2174° / 52°0
74 °
Alton, Wednesday, 21 October
Overcast. High 74°, low 52°.
Pressure30.24 inHg
Wind10.4 mph S
Humidity21%
Visibility—
Dew point27°
Thu, 2277° / 56°0
77 °
Alton, Thursday, 22 October
Mostly clear. High 77°, low 56°.
Pressure30.21 inHg
Wind7.6 mph S
Humidity23%
Visibility—
Dew point32°
Fri, 2379° / 58°0
79 °
Alton, Friday, 23 October
Mostly clear. High 79°, low 58°.
Pressure30.15 inHg
Wind7.5 mph SW
Humidity29%
Visibility—
Dew point40°
Sat, 2481° / 60°0
81 °
Alton, Saturday, 24 October
Clear. High 81°, low 60°.
Pressure30.12 inHg
Wind5.6 mph W
Humidity43%
Visibility—
Dew point52°
Sun, 2584° / 64°0.12
84 °
Alton, Sunday, 25 October
Light rain. High 84°, low 64°.
Pressure29.94 inHg
Wind12.6 mph SW
Humidity43%
Visibility—
Dew point55°
Mon, 2659° / 47°0
59 °
Alton, Monday, 26 October
Overcast. High 59°, low 47°.
Pressure29.97 inHg
Wind14.8 mph NW
Humidity41%
Visibility—
Dew point32°
From day 17 onward the outlook is built from 60-year climate statistics
Tue, 2762° / 47°0.1
62 °
Alton, Tuesday, 27 October
Climate normal for this date — 60-year average.
Average high62°
Average low47°
Average precipitation0.1 in
Chance of precipitation23%
Record high79° (2023)
Record low33° (2001)
Wed, 2861° / 46°0.05
61 °
Alton, Wednesday, 28 October
Climate normal for this date — 60-year average.
Average high61°
Average low46°
Average precipitation0.05 in
Chance of precipitation22%
Record high78° (1999)
Record low32° (1969)
Thu, 2961° / 46°0.11
61 °
Alton, Thursday, 29 October
Climate normal for this date — 60-year average.
Average high61°
Average low46°
Average precipitation0.11 in
Chance of precipitation30%
Record high81° (2004)
Record low31° (1980)
Fri, 3063° / 47°0.12
63 °
Alton, Friday, 30 October
Climate normal for this date — 60-year average.
Average high63°
Average low47°
Average precipitation0.12 in
Chance of precipitation30%
Record high79° (1971)
Record low29° (1980)
Sat, 3162° / 47°0.15
62 °
Alton, Saturday, 31 October
Climate normal for this date — 60-year average.
Average high62°
Average low47°
Average precipitation0.15 in
Chance of precipitation38%
Record high79° (1968)
Record low29° (1993)
Sun, 0161° / 46°0.18
61 °
Alton, Sunday, 1 November
Climate normal for this date — 60-year average.
Average high61°
Average low46°
Average precipitation0.18 in
Chance of precipitation30%
Record high79° (2016)
Record low27° (1993)
Mon, 0260° / 45°0.08
60 °
Alton, Monday, 2 November
Climate normal for this date — 60-year average.
Average high60°
Average low45°
Average precipitation0.08 in
Chance of precipitation30%
Record high79° (2016)
Record low27° (1966)
Tue, 0358° / 44°0.11
58 °
Alton, Tuesday, 3 November
Climate normal for this date — 60-year average.
Average high58°
Average low44°
Average precipitation0.11 in
Chance of precipitation30%
Record high78° (1987)
Record low20° (1991)
Wed, 0457° / 45°0.16
57 °
Alton, Wednesday, 4 November
Climate normal for this date — 60-year average.
Average high57°
Average low45°
Average precipitation0.16 in
Chance of precipitation28%
Record high76° (2022)
Record low20° (1991)
Thu, 0558° / 43°0.16
58 °
Alton, Thursday, 5 November
Climate normal for this date — 60-year average.
Average high58°
Average low43°
Average precipitation0.16 in
Chance of precipitation30%
Record high76° (1978)
Record low24° (1991)
Fri, 0657° / 42°0.09
57 °
Alton, Friday, 6 November
Climate normal for this date — 60-year average.
Average high57°
Average low42°
Average precipitation0.09 in
Chance of precipitation33%
Record high77° (2023)
Record low28° (1982)
Sat, 0757° / 42°0.08
57 °
Alton, Saturday, 7 November
Climate normal for this date — 60-year average.
Average high57°
Average low42°
Average precipitation0.08 in
Chance of precipitation22%
Record high74° (1980)
Record low17° (1991)
Sun, 0857° / 42°0.04
57 °
Alton, Sunday, 8 November
Climate normal for this date — 60-year average.
Average high57°
Average low42°
Average precipitation0.04 in
Chance of precipitation17%
Record high80° (2023)
Record low4° (1991)
Mon, 0958° / 43°0.1
58 °
Alton, Monday, 9 November
Climate normal for this date — 60-year average.
Average high58°
Average low43°
Average precipitation0.1 in
Chance of precipitation30%
Record high76° (2022)
Record low8° (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 Alton, 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 Alton, 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.