| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 3.3° | -7.1° | 21.5mm | 6.1 | 21 |
| February | 2.2° | -8.6° | 20.5mm | 8.5 | 13 |
| March | 9.3° | -3.4° | 16.2mm | 6.2 | 45 |
| April | 14.3° | 0.8° | 54.1mm | 9.2 | 62 |
| May | 19.5° | 5.4° | 65.4mm | 10.8 | 77 |
| June | 24.6° | 9.8° | 59.2mm | 9.2 | 82 |
| July | 30.7° | 13.2° | 28.8mm | 6.1 | 73 |
| August | 29° | 11.8° | 35mm | 6.2 | 80 |
| September | 22.9° | 7.4° | 41.5mm | 7.1 | 86 |
| October | 15.3° | 2.5° | 27mm | 6.8 | 71 |
| November | 7.9° | -2.9° | 20.3mm | 5.9 | 42 |
| December | 1.8° | -7.8° | 19.3mm | 6.3 | 18 |
January in Great Falls averages a daily high of 3.3°C with nights around -7.1°C. Expect roughly 6.1 wet days totalling 21.5mm. A hard month to visit for comfort alone.
February in Great Falls averages a daily high of 2.2°C with nights around -8.6°C. Expect roughly 8.5 wet days totalling 20.5mm. A hard month to visit for comfort alone.
March in Great Falls averages a daily high of 9.3°C with nights around -3.4°C. Expect roughly 6.2 wet days totalling 16.2mm. Demanding conditions — pack for it and plan indoor options.
April in Great Falls averages a daily high of 14.3°C with nights around 0.8°C. Expect roughly 9.2 wet days totalling 54.1mm. Generally workable, with some weather to plan around.
May in Great Falls averages a daily high of 19.5°C with nights around 5.4°C. Expect roughly 10.8 wet days totalling 65.4mm. Comfortable conditions for being outdoors all day.
June in Great Falls averages a daily high of 24.6°C with nights around 9.8°C. Expect roughly 9.2 wet days totalling 59.2mm. Comfortable conditions for being outdoors all day.
July in Great Falls averages a daily high of 30.7°C with nights around 13.2°C. Expect roughly 6.1 wet days totalling 28.8mm. Generally workable, with some weather to plan around.
August in Great Falls averages a daily high of 29°C with nights around 11.8°C. Expect roughly 6.2 wet days totalling 35mm. Comfortable conditions for being outdoors all day.
September in Great Falls averages a daily high of 22.9°C with nights around 7.4°C. Expect roughly 7.1 wet days totalling 41.5mm. Comfortable conditions for being outdoors all day.
October in Great Falls averages a daily high of 15.3°C with nights around 2.5°C. Expect roughly 6.8 wet days totalling 27mm. Generally workable, with some weather to plan around.
November in Great Falls averages a daily high of 7.9°C with nights around -2.9°C. Expect roughly 5.9 wet days totalling 20.3mm. Demanding conditions — pack for it and plan indoor options.
December in Great Falls averages a daily high of 1.8°C with nights around -7.8°C. Expect roughly 6.3 wet days totalling 19.3mm. A hard month to visit for comfort alone.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Great Falls peaks at 86.
Based on 30 years of records, August–September scores highest for comfort in Great Falls, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 30.7°C.
May is the wettest, averaging 65.4mm of rain across roughly 10.8 wet days.
December is the coolest month, with average daily highs around 1.8°C.