Monthly outlook for Port Byron, IL: average high 61.1°, average low 47.5°. That is 2.6° above the climate normal for October. Precipitation is expected on 6 days (about 1.8 inches), against a normal of 5 days and 1.6 inches. The warmest day looks like 22 October (76.2°), the coolest 30 October (34.9°).
61.1°/47.5°
Average high / low
+2.6°
Above normal
6 / 5
Wet days / normal
1.8 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
21 October – 30 October
64.6°
57.9°
+3.7°
31 October – 9 November
55.2°
53°
+1.2°
10 November – 19 November
at normal
47.8°
—
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).
Thu, 2276° / 49°0
76 °
Port Byron, Thursday, 22 October
Clear. High 76°, low 49°.
Pressure30.27 inHg
Wind2.7 mph S
Humidity60%
Visibility6.2 mi
Dew point55°
Fri, 2372° / 50°0
72 °
Port Byron, Friday, 23 October
Clear. High 72°, low 50°.
Pressure30.30 inHg
Wind6.3 mph S
Humidity55%
Visibility6.2 mi
Dew point53°
Sat, 2470° / 52°0
70 °
Port Byron, Saturday, 24 October
Overcast. High 70°, low 52°.
Pressure30.33 inHg
Wind8.9 mph S
Humidity56%
Visibility6.2 mi
Dew point51°
Sun, 2572° / 52°0
72 °
Port Byron, Sunday, 25 October
Overcast. High 72°, low 52°.
Pressure30.36 inHg
Wind4.3 mph S
Humidity58%
Visibility6.2 mi
Dew point51°
Mon, 2670° / 54°0
70 °
Port Byron, Monday, 26 October
Overcast. High 70°, low 54°.
Pressure30.24 inHg
Wind7.9 mph S
Humidity56%
Visibility—
Dew point50°
Tue, 2758° / 52°0.18
58 °
Port Byron, Tuesday, 27 October
Light rain. High 58°, low 52°.
Pressure30.21 inHg
Wind8.8 mph SE
Humidity88%
Visibility—
Dew point50°
Wed, 2855° / 43°0.52
55 °
Port Byron, Wednesday, 28 October
Rain. High 55°, low 43°.
Pressure30.03 inHg
Wind17.8 mph NW
Humidity93%
Visibility—
Dew point47°
Thu, 2949° / 38°0
49 °
Port Byron, Thursday, 29 October
Clear. High 49°, low 38°.
Pressure30.36 inHg
Wind12.3 mph N
Humidity52%
Visibility—
Dew point29°
Fri, 3051° / 35°0.02
51 °
Port Byron, Friday, 30 October
Light rain. High 51°, low 35°.
Pressure30.18 inHg
Wind10.6 mph S
Humidity49%
Visibility—
Dew point29°
Sat, 3166° / 50°0
66 °
Port Byron, Saturday, 31 October
Overcast. High 66°, low 50°.
Pressure29.97 inHg
Wind12.8 mph S
Humidity63%
Visibility—
Dew point49°
Sun, 0159° / 54°0.06
59 °
Port Byron, Sunday, 1 November
Light rain. High 59°, low 54°.
Pressure30.21 inHg
Wind10.3 mph E
Humidity64%
Visibility—
Dew point46°
Mon, 0255° / 54°0.79
55 °
Port Byron, Monday, 2 November
Rain. High 55°, low 54°.
Pressure29.85 inHg
Wind13.4 mph E
Humidity98%
Visibility—
Dew point54°
Tue, 0354° / 46°0.16
54 °
Port Byron, Tuesday, 3 November
Light rain. High 54°, low 46°.
Pressure29.94 inHg
Wind20 mph NE
Humidity87%
Visibility—
Dew point49°
Wed, 0446° / 44°0.07
46 °
Port Byron, Wednesday, 4 November
Light rain. High 46°, low 44°.
Pressure30.30 inHg
Wind19.8 mph NE
Humidity80%
Visibility—
Dew point38°
Thu, 0551° / 45°0
51 °
Port Byron, Thursday, 5 November
Light rain. High 51°, low 45°.
Pressure30.12 inHg
Wind5.7 mph NE
Humidity67%
Visibility—
Dew point39°
From day 17 onward the outlook is built from 60-year climate statistics
Fri, 0652° / 38°0.08
52 °
Port Byron, Friday, 6 November
Climate normal for this date — 60-year average.
Average high52°
Average low38°
Average precipitation0.08 in
Chance of precipitation28%
Record high71° (2020)
Record low21° (1991)
Sat, 0752° / 37°0.02
52 °
Port Byron, Saturday, 7 November
Climate normal for this date — 60-year average.
Average high52°
Average low37°
Average precipitation0.02 in
Chance of precipitation15%
Record high69° (1966)
Record low13° (1991)
Sun, 0852° / 37°0.04
52 °
Port Byron, Sunday, 8 November
Climate normal for this date — 60-year average.
Average high52°
Average low37°
Average precipitation0.04 in
Chance of precipitation15%
Record high75° (1999)
Record low12° (1991)
Mon, 0951° / 37°0.11
51 °
Port Byron, Monday, 9 November
Climate normal for this date — 60-year average.
Average high51°
Average low37°
Average precipitation0.11 in
Chance of precipitation33%
Record high74° (1999)
Record low17° (1991)
Tue, 1050° / 35°0.1
50 °
Port Byron, Tuesday, 10 November
Climate normal for this date — 60-year average.
Average high50°
Average low35°
Average precipitation0.1 in
Chance of precipitation28%
Record high73° (2022)
Record low15° (2018)
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)
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.