Monthly outlook for Port Byron, IL: average high 58.3°, average low 45.6°. That is 2.4° above the climate normal for October. Precipitation is expected on 8 days (about 3.0 inches), against a normal of 4 days and 1.4 inches. The warmest day looks like 28 October (75.1°), the coolest 7 November (27.8°).
58.3°/45.6°
Average high / low
+2.4°
Above normal
8 / 4
Wet days / normal
3.0 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
26 October – 4 November
65.9°
55.4°
+5.8°
5 November – 14 November
45.5°
49.8°
-2.4°
15 November – 24 November
at normal
46.1°
—
October records over 66 years
88.2°3 October 2025All-time high
17.8°28 October 1967All-time low
Climate normals and records are computed from the nearest reference point — Princeton (4 mi).
Tue, 2772° / 51°0
72 °
Port Byron, Tuesday, 27 October
Overcast. High 72°, low 51°.
Pressure30.21 inHg
Wind5.4 mph SE
Humidity69%
Visibility6.2 mi
Dew point52°
Wed, 2875° / 54°0
75 °
Port Byron, Wednesday, 28 October
Overcast. High 75°, low 54°.
Pressure30.15 inHg
Wind7.3 mph S
Humidity60%
Visibility6.2 mi
Dew point54°
Thu, 2968° / 53°0.06
68 °
Port Byron, Thursday, 29 October
Light rain. High 68°, low 53°.
Pressure30.09 inHg
Wind7.6 mph W
Humidity83%
Visibility6.2 mi
Dew point60°
Fri, 3065° / 45°0.05
65 °
Port Byron, Friday, 30 October
Light rain. High 65°, low 45°.
Pressure30.24 inHg
Wind6.1 mph SE
Humidity63%
Visibility6.2 mi
Dew point48°
Sat, 3165° / 55°0.41
65 °
Port Byron, Saturday, 31 October
Rain. High 65°, low 55°.
Pressure30.12 inHg
Wind6.8 mph SW
Humidity81%
Visibility—
Dew point58°
Sun, 0165° / 55°0.13
65 °
Port Byron, Sunday, 1 November
Rain. High 65°, low 55°.
Pressure29.97 inHg
Wind7 mph N
Humidity70%
Visibility—
Dew point54°
Mon, 0260° / 52°0.02
60 °
Port Byron, Monday, 2 November
Light rain. High 60°, low 52°.
Pressure29.83 inHg
Wind16.4 mph E
Humidity73%
Visibility—
Dew point50°
Tue, 0362° / 56°0.9
62 °
Port Byron, Tuesday, 3 November
Rain. High 62°, low 56°.
Pressure29.77 inHg
Wind20.9 mph SE
Humidity91%
Visibility—
Dew point59°
Wed, 0460° / 48°1.23
60 °
Port Byron, Wednesday, 4 November
Heavy rain. High 60°, low 48°.
Pressure29.44 inHg
Wind39.1 mph SW
Humidity79%
Visibility—
Dew point48°
Thu, 0548° / 35°0.06
48 °
Port Byron, Thursday, 5 November
Light rain. High 48°, low 35°.
Pressure29.59 inHg
Wind24.7 mph NW
Humidity76%
Visibility—
Dew point33°
Fri, 0638° / 31°0.02
38 °
Port Byron, Friday, 6 November
Snow. High 38°, low 31°.
Pressure29.88 inHg
Wind21.1 mph NW
Humidity63%
Visibility—
Dew point25°
Sat, 0741° / 28°0
41 °
Port Byron, Saturday, 7 November
Clear. High 41°, low 28°.
Pressure30.12 inHg
Wind11.7 mph NW
Humidity43%
Visibility—
Dew point17°
Sun, 0847° / 31°0
47 °
Port Byron, Sunday, 8 November
Overcast. High 47°, low 31°.
Pressure30.06 inHg
Wind14.6 mph S
Humidity47%
Visibility—
Dew point23°
Mon, 0952° / 46°0.13
52 °
Port Byron, Monday, 9 November
Light rain. High 52°, low 46°.
Pressure29.62 inHg
Wind15.7 mph S
Humidity93%
Visibility—
Dew point47°
Tue, 1047° / 39°0
47 °
Port Byron, Tuesday, 10 November
Overcast. High 47°, low 39°.
Pressure29.77 inHg
Wind11.6 mph W
Humidity62%
Visibility—
Dew point33°
From day 17 onward the outlook is built from 60-year climate statistics
Wed, 1148° / 33°0.07
48 °
Port Byron, Wednesday, 11 November
Climate normal for this date — 60-year average.
Average high48°
Average low33°
Average precipitation0.07 in
Chance of precipitation22%
Record high72° (1964)
Record low15° (2019)
Thu, 1246° / 32°0.06
46 °
Port Byron, Thursday, 12 November
Climate normal for this date — 60-year average.
Average high46°
Average low32°
Average precipitation0.06 in
Chance of precipitation25%
Record high66° (1964)
Record low7° (2019)
Fri, 1347° / 32°0.05
47 °
Port Byron, Friday, 13 November
Climate normal for this date — 60-year average.
Average high47°
Average low32°
Average precipitation0.05 in
Chance of precipitation25%
Record high72° (1999)
Record low6° (1986)
Sat, 1448° / 33°0.06
48 °
Port Byron, Saturday, 14 November
Climate normal for this date — 60-year average.
Average high48°
Average low33°
Average precipitation0.06 in
Chance of precipitation28%
Record high70° (2025)
Record low14° (1986)
Sun, 1547° / 34°0.07
47 °
Port Byron, Sunday, 15 November
Climate normal for this date — 60-year average.
Average high47°
Average low34°
Average precipitation0.07 in
Chance of precipitation28%
Record high69° (2025)
Record low18° (1982)
Mon, 1648° / 33°0.06
48 °
Port Byron, Monday, 16 November
Climate normal for this date — 60-year average.
Average high48°
Average low33°
Average precipitation0.06 in
Chance of precipitation25%
Record high66° (1971)
Record low17° (1997)
Tue, 1748° / 34°0.13
48 °
Port Byron, Tuesday, 17 November
Climate normal for this date — 60-year average.
Average high48°
Average low34°
Average precipitation0.13 in
Chance of precipitation25%
Record high73° (2016)
Record low14° (2005)
Wed, 1848° / 34°0.07
48 °
Port Byron, Wednesday, 18 November
Climate normal for this date — 60-year average.
Average high48°
Average low34°
Average precipitation0.07 in
Chance of precipitation30%
Record high70° (1999)
Record low11° (2014)
Thu, 1948° / 33°0.06
48 °
Port Byron, Thursday, 19 November
Climate normal for this date — 60-year average.
Average high48°
Average low33°
Average precipitation0.06 in
Chance of precipitation27%
Record high66° (1979)
Record low16° (2022)
Fri, 2046° / 32°0.1
46 °
Port Byron, Friday, 20 November
Climate normal for this date — 60-year average.
Average high46°
Average low32°
Average precipitation0.1 in
Chance of precipitation32%
Record high65° (2003)
Record low16° (2022)
Sat, 2144° / 30°0.08
44 °
Port Byron, Saturday, 21 November
Climate normal for this date — 60-year average.
Average high44°
Average low30°
Average precipitation0.08 in
Chance of precipitation22%
Record high66° (1990)
Record low7° (1964)
Sun, 2245° / 30°0.03
45 °
Port Byron, Sunday, 22 November
Climate normal for this date — 60-year average.
Average high45°
Average low30°
Average precipitation0.03 in
Chance of precipitation15%
Record high67° (2010)
Record low4° (2015)
Mon, 2344° / 31°0.08
44 °
Port Byron, Monday, 23 November
Climate normal for this date — 60-year average.
Average high44°
Average low31°
Average precipitation0.08 in
Chance of precipitation30%
Record high65° (1966)
Record low11° (1970)
Tue, 2443° / 29°0.08
43 °
Port Byron, Tuesday, 24 November
Climate normal for this date — 60-year average.
Average high43°
Average low29°
Average precipitation0.08 in
Chance of precipitation25%
Record high64° (1966)
Record low8° (1985)
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 Port Byron, 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 Port Byron, 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.