Monthly outlook for Grannis, MT: average high 55.1°, average low 36.6°. That is 1.4° above the climate normal for October. Precipitation is expected on 4 days (about 1.8 inches), against a normal of 4 days and 0.9 inches. The warmest day looks like 23 October (68.9°), the coolest 13 October (27.6°).
55.1°/36.6°
Average high / low
+1.4°
Above normal
4 / 4
Wet days / normal
1.8 in
Precipitation this month
Ten-day blocks vs climate normal
Period
Forecast high
Normal
Difference
10 October – 19 October
53.4°
53.3°
+0.1°
20 October – 29 October
58°
49.8°
+4.6°
30 October – 8 November
at normal
43.4°
—
October records over 66 years
83.1°1 October 2011All-time high
-12.3°10 October 2009All-time low
Climate normals and records are computed from the nearest reference point — Clyde Park (10 mi).
Sun, 1145° / 36°0.51
45 °
Grannis, Sunday, 11 October
Snow. High 45°, low 36°.
Pressure29.91 inHg
Wind8.1 mph SE
Humidity94%
Visibility3.3 mi
Dew point36°
Mon, 1236° / 28°0.22
36 °
Grannis, Monday, 12 October
Snow. High 36°, low 28°.
Pressure30.12 inHg
Wind0.4 mph SE
Humidity91%
Visibility6.2 mi
Dew point30°
Tue, 1346° / 28°0
46 °
Grannis, Tuesday, 13 October
Mostly clear. High 46°, low 28°.
Pressure30.06 inHg
Wind3.4 mph NW
Humidity69%
Visibility—
Dew point31°
Wed, 1449° / 33°0
49 °
Grannis, Wednesday, 14 October
Overcast. High 49°, low 33°.
Pressure30.18 inHg
Wind6.3 mph S
Humidity58%
Visibility6.2 mi
Dew point32°
Thu, 1558° / 33°0
58 °
Grannis, Thursday, 15 October
Clear. High 58°, low 33°.
Pressure30.39 inHg
Wind9.2 mph NW
Humidity43%
Visibility—
Dew point29°
Fri, 1647° / 32°0
47 °
Grannis, Friday, 16 October
Mostly clear. High 47°, low 32°.
Pressure30.65 inHg
Wind5.8 mph E
Humidity48%
Visibility—
Dew point22°
Sat, 1762° / 31°0
62 °
Grannis, Saturday, 17 October
Overcast. High 62°, low 31°.
Pressure30.09 inHg
Wind7.9 mph W
Humidity34%
Visibility—
Dew point25°
Sun, 1868° / 41°0
68 °
Grannis, Sunday, 18 October
Partly cloudy. High 68°, low 41°.
Pressure29.94 inHg
Wind9.2 mph SW
Humidity36%
Visibility—
Dew point31°
Mon, 1961° / 44°0.02
61 °
Grannis, Monday, 19 October
Light rain. High 61°, low 44°.
Pressure29.85 inHg
Wind7.9 mph S
Humidity38%
Visibility—
Dew point30°
Tue, 2047° / 37°0.81
47 °
Grannis, Tuesday, 20 October
Rain. High 47°, low 37°.
Pressure30.12 inHg
Wind10.8 mph W
Humidity67%
Visibility—
Dew point33°
Wed, 2157° / 34°0
57 °
Grannis, Wednesday, 21 October
Mostly clear. High 57°, low 34°.
Pressure30.00 inHg
Wind21.2 mph W
Humidity42%
Visibility—
Dew point27°
Thu, 2256° / 34°0
56 °
Grannis, Thursday, 22 October
Overcast. High 56°, low 34°.
Pressure30.06 inHg
Wind8 mph SW
Humidity45%
Visibility—
Dew point27°
Fri, 2369° / 40°0
69 °
Grannis, Friday, 23 October
Overcast. High 69°, low 40°.
Pressure29.88 inHg
Wind12.6 mph SW
Humidity39%
Visibility—
Dew point31°
Sat, 2461° / 45°0
61 °
Grannis, Saturday, 24 October
Overcast. High 61°, low 45°.
Pressure30.06 inHg
Wind12 mph W
Humidity33%
Visibility—
Dew point29°
Sun, 2558° / 42°0
58 °
Grannis, Sunday, 25 October
Clear. High 58°, low 42°.
Pressure30.30 inHg
Wind6.1 mph E
Humidity49%
Visibility—
Dew point33°
From day 17 onward the outlook is built from 60-year climate statistics
Mon, 2649° / 31°0.07
49 °
Grannis, Monday, 26 October
Climate normal for this date — 60-year average.
Average high49°
Average low31°
Average precipitation0.07 in
Chance of precipitation35%
Record high65° (1999)
Record low-4° (2020)
Tue, 2748° / 29°0.04
48 °
Grannis, Tuesday, 27 October
Climate normal for this date — 60-year average.
Average high48°
Average low29°
Average precipitation0.04 in
Chance of precipitation25%
Record high68° (2024)
Record low2° (2019)
Wed, 2847° / 29°0.06
47 °
Grannis, Wednesday, 28 October
Climate normal for this date — 60-year average.
Average high47°
Average low29°
Average precipitation0.06 in
Chance of precipitation27%
Record high65° (1987)
Record low4° (1971)
Thu, 2945° / 28°0.06
45 °
Grannis, Thursday, 29 October
Climate normal for this date — 60-year average.
Average high45°
Average low28°
Average precipitation0.06 in
Chance of precipitation28%
Record high65° (1987)
Record low-8° (2019)
Fri, 3045° / 27°0.04
45 °
Grannis, Friday, 30 October
Climate normal for this date — 60-year average.
Average high45°
Average low27°
Average precipitation0.04 in
Chance of precipitation25%
Record high66° (1987)
Record low-10° (1972)
Sat, 3144° / 26°0.06
44 °
Grannis, Saturday, 31 October
Climate normal for this date — 60-year average.
Average high44°
Average low26°
Average precipitation0.06 in
Chance of precipitation27%
Record high64° (2014)
Record low-12° (2002)
Sun, 0144° / 26°0.06
44 °
Grannis, Sunday, 1 November
Climate normal for this date — 60-year average.
Average high44°
Average low26°
Average precipitation0.06 in
Chance of precipitation25%
Record high67° (2025)
Record low-3° (1989)
Mon, 0243° / 26°0.03
43 °
Grannis, Monday, 2 November
Climate normal for this date — 60-year average.
Average high43°
Average low26°
Average precipitation0.03 in
Chance of precipitation25%
Record high61° (2020)
Record low-10° (1995)
Tue, 0344° / 27°0.04
44 °
Grannis, Tuesday, 3 November
Climate normal for this date — 60-year average.
Average high44°
Average low27°
Average precipitation0.04 in
Chance of precipitation22%
Record high63° (2020)
Record low-1° (1995)
Wed, 0444° / 27°0.05
44 °
Grannis, Wednesday, 4 November
Climate normal for this date — 60-year average.
Average high44°
Average low27°
Average precipitation0.05 in
Chance of precipitation30%
Record high61° (2020)
Record low-6° (1973)
Thu, 0544° / 27°0.06
44 °
Grannis, Thursday, 5 November
Climate normal for this date — 60-year average.
Average high44°
Average low27°
Average precipitation0.06 in
Chance of precipitation38%
Record high66° (2020)
Record low-5° (2003)
Fri, 0643° / 26°0.05
43 °
Grannis, Friday, 6 November
Climate normal for this date — 60-year average.
Average high43°
Average low26°
Average precipitation0.05 in
Chance of precipitation27%
Record high62° (1999)
Record low2° (2003)
Sat, 0742° / 26°0.04
42 °
Grannis, Saturday, 7 November
Climate normal for this date — 60-year average.
Average high42°
Average low26°
Average precipitation0.04 in
Chance of precipitation33%
Record high61° (1999)
Record low1° (2017)
Sun, 0842° / 24°0.08
42 °
Grannis, Sunday, 8 November
Climate normal for this date — 60-year average.
Average high42°
Average low24°
Average precipitation0.08 in
Chance of precipitation37%
Record high61° (1999)
Record low0° (2018)
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 Grannis, MT 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 Grannis, MT 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.