Great Falls, MT weather in May
Expect cool weather with frequent rain in Great Falls in May, with highs near 65°F and lows near 38°F. Rain or snow falls on about 11 days. Snowfall averages about 1.9 in. Great for outdoor plans.
- Normal high
- 65°F
- Normal low
- 38°F
- Wet days
- 11
- 2.4 in total
- Snowfall
- 1.9 in
- snow on the ground 1 day
How May changes from start to finish
| May 1 | May 31 | |
|---|---|---|
| Normal high | 60°F | 69°F |
| Normal low | 33°F | 43°F |
| Chance of a wet day | 34% | 41% |
| Sunrise / sunset | 6:08 am / 8:36 pm | 5:32 am / 9:13 pm |
| Daylight | 14.5 h | 15.7 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Mountain Time).
A typical May day
- 6 am44°Fdew point 36°F
- 9 am53°Fdew point 37°F
- Noon59°Fdew point 35°F
- 3 pm62°Fdew point 35°F
- 6 pm60°Fdew point 35°F
- 9 pm51°Fdew point 36°F
NOAA hourly normals (local standard time) from Great Falls Intl Airport (4 mi away); average wind 10 mph; clear or few clouds in 51% of daytime hours, mostly cloudy or overcast in 38%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F14 of 31
- Hot dayshigh 90°F or more0 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow11 of 31
- Notable rainat least 0.10 in6 of 31
- Freezing nightslow 32°F or below6 of 31
- Snow on the groundsnow depth 1 in or more1 of 31
Average days per May, counted from daily records for each year 1991-2020.
Rain and snow in May
Normal precipitation is 2.4 in; a dry May brings about 2.0 in and a wet one about 2.9 in (25th and 75th percentiles). About 1 day brings half an inch or more. Normal snowfall is 1.9 in, with about 1 day of an inch or more.
How May varies from year to year
- Warmest May, 1991-20202001: average high 71°F
- Coolest May1996: average high 58°F
- Wettest May2011: 4.1 in
- Driest May2001: 0.5 in
- Highest reading90°F (May 18, 2006)
- Lowest reading12°F (May 1, 2009)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
May compared with April and June
| April | May | June | |
|---|---|---|---|
| Normal high | 55°F | 65°F | 73°F |
| Normal low | 30°F | 38°F | 46°F |
| Wet days | 10 | 11 | 12 |
| Comfortable days | 6 | 14 | 18 |
| Daylight | 13.7 h | 15.1 h | 15.9 h |
Highs change by +10°F from April and +8°F into June.
Nearby alternatives in May
- Cooler: Big Sky, MT153 mi · high 58°F · 14 wet days
How Great Falls ranks in May
- Normal high341st warmest of 378 cities; 4th of 6 in Montana
- Wet days238th driest of 378
- Comfortable days145th most of 339
What to pack for Great Falls in May
- A warm jacket – lows near 38°F, highs near 65°F
- Layers – afternoons near 65°F but nights near 38°F
- A rain jacket or umbrella – rain or snow on about 11 days
Frost in May
The last spring frost typically comes around May 19; in 1 year in 10 it comes after Jun 2. All frost dates for Great Falls.
Heating and cooling
May has 422 heating degree days and 3 cooling degree days (base 65°F), 5% of the year's total heating and cooling demand.
Questions
How cold is Great Falls in May?
The normal high is 65°F and the normal low is 38°F. From 1991 to 2020 the coldest May reading was 12°F (May 1, 2009).
Does it rain a lot in Great Falls in May?
About 11 days in May have at least 0.01 in of precipitation, and the normal total is 2.4 in. The wettest May in 1991-2020 was in 2011 (4.1 in); the driest was in 2001 (0.5 in).
Does it snow in Great Falls in May?
Yes. Normal snowfall in May is 1.9 in, and snow covers the ground on about 1 day.
Is May a good time to visit Great Falls?
May ranks 2nd of 12 months on our comfort score for Great Falls (73 out of 100). It has about 14 comfortable days. The best month is June.
Where the numbers come from
- Temperature, rain, snowfall, snow depth, frost dates, humidity and wind by hour and cloud cover: Great Falls Intl Airport (USW00024143), 4.2 mi WSW of the city center, 3,664 ft (335 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Great Falls International Airport (727750-24143), 4.3 mi WSW of the city center, 3,667 ft (338 ft higher than the city). Hourly observations, 1991-2020.