May weather forecast
Great Falls, MT

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A far view from on top of the vast Missouri River of the City of Lights, Great Falls, Montana
A far view from on top of the vast Missouri River of the City of Lights, Great Falls, Montana

Weather in May

May sees a noticeable increase in humidity and rainfall. The bout of precipitation is highest in this month accumulating as much as 0.63" (16mm) of rain. A comparative analysis of the declining period from May to June reveals a continued escalation in temperature, but a decrease in rainfall. Lavender blooms often peak during this month, and a visit to the local farmers’ market is a popular activity. Parks and trails are commonly explored amidst the comfortable weather.

Temperature

May marks a rise in the average high-temperature, moving from April's cool 52.3°F (11.3°C) to an enjoyable 63°F (17.2°C). In the month of May, the average low-temperature usually rests at a wintry 42.6°F (5.9°C).

Humidity

In May, the average relative humidity is 59%.

Rainfall

In May, the rain falls for 9 days. Throughout May, 0.63" (16mm) of precipitation is accumulated. In Great Falls, during the entire year, the rain falls for 68.2 days and collects up to 4.49" (114mm) of precipitation.

Snowfall

Months with snowfall are January through May, September through December. May is the last month it regularly snows in Great Falls. During 0.9 snowfall days, in May, Great Falls aggregates 0.31" (8mm) of snow. Throughout the year, there are 45.4 snowfall days, and 11.61" (295mm) of snow is accumulated.

Daylight

The average length of the day in May is 15h and 9min.
On the first day of the month, sunrise is at 6:06 am and sunset at 8:37 pm. On the last day of May, sunrise is at 5:31 am and sunset at 9:14 pm MDT.

Sunshine

In Great Falls, the average sunshine in May is 10.3h.

UV index

In Great Falls, the average daily maximum UV index in May is 4. A UV Index reading of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for the average person.
Note: The maximum UV index of 4 during May translates into these guidelines:
Take precautions. Light skin individuals may get burned in less than 30 minutes. It's crucial to reduce time in the direct Sun around mid-day due to the intense solar radiation. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days. Consider carefully! The reflective quality of snow can almost double the intensity of the Sun's UV radiation.

Frequently asked questions

What is the usual temperature for Great Falls in May?

During May, Great Falls experiences an average high-temperature of 63°F (17.2°C) and a low-temperature of 42.6°F (5.9°C).

What is the average humidity in May?

In May, the average relative humidity is 59%.

How many days does it rain in May?

In May, the rain falls for 9 days. Throughout May, 0.63" (16mm) of precipitation is accumulated.

What is the last month it snows?

May is the last month it regularly snows. During 0.9 snowfall days, in May, Great Falls aggregates 0.31" (8mm) of snow.

How many hours of daylight does Great Falls have in May?

The average day length in May is 15h and 9min.

When is the sunrise / sunset in May?

In May, on the first day of the month, sunrise is at 6:06 am and sunset at 8:37 pm. On the last day of the month, sunrise is at 5:31 am and sunset at 9:14 pm MDT.

How long on average sun shines in May?

The average sunshine duration in May in Great Falls is 10.3h.

How high is the UV index in May?

The average daily maximum UV index in May is 4. A UV Index reading of 3 to 5 represents a moderate vulnerability from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in May
Great Falls, MT

Average temperature in May - Great Falls, MT
  • Average high temperature in May: 63°F

The warmest month (with the highest average high temperature) is July (83.1°F).
The month with the lowest average high temperature is December (30°F).

  • Average low temperature in May: 42.6°F

The month with the highest average low temperature is August (57.7°F).
The coldest months (with the lowest average low temperature) are February and December (18.3°F).

Average pressure in May
Great Falls, MT

Average pressure in May - Great Falls, MT
  • Average pressure in May: 29.93"Hg

The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.87"Hg).

Average wind speed in May
Great Falls, MT

Average wind speed in May - Great Falls, MT
  • Average wind speed in May: 8.5mph

The windiest month (with the highest average wind speed) is November (11.4mph).
The calmest month (with the lowest average wind speed) is August (7.7mph).

Average humidity in May
Great Falls, MT

Average humidity in May - Great Falls, MT
  • Average humidity in May: 59%

The month with the highest relative humidity is January (77%).
The month with the lowest relative humidity is August (40%).

Average rainfall in May
Great Falls, MT

Average rainfall in May - Great Falls, MT
  • Average rainfall in May: 0.63"

The wettest month (with the highest rainfall) is June (0.87").
The driest month (with the least rainfall) is December (0.16").

Average rainfall days in May
Great Falls, MT

Average rainfall days in May - Great Falls, MT
  • Average rainfall days in May: 9 days

The month with the highest number of rainy days is April (9.9 days).
The month with the least rainy days is December (2.7 days).

Average snowfall in May
Great Falls, MT

Average snowfall in May - Great Falls, MT
  • Average snowfall in May: 0.31"

The month with the highest snowfall is February (2.09").
The months with the least snowfall are June, July and August (0").

Average snowfall days in May
Great Falls, MT

Average snowfall days in May - Great Falls, MT
  • Average snowfall days in May: 0.9 days

The month with the highest number of snowfall days is February (10 days).
The months with the least snowfall days are June, July and August (0 days).

Average daylight in May /
Average sunshine in May
Great Falls, MT

Average daylight in May / Average sunshine in May - Great Falls, MT
  • Average daylight in May: 15h and 1min

The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).

  • Average sunshine in May: 10h and 2min

The month with the most sunshine is July (Average sunshine: 12h and 6min).
The months with the least sunshine are January, February and December (Average sunshine: 5h and 30min).

Average sunshine days in May
Great Falls, MT

Average sunshine days in May - Great Falls, MT
  • Average sunshine days in May: 20.3 days

The month with the most sunshine days is July (26.1 days).
The months with the least sunshine days are February and April (16.2 days).

Average UV index in May
Great Falls, MT

Average UV index in May - Great Falls, MT
  • Average UV index in May: 4

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, March, October, November and December (UV index 2).

Average cloud cover in May
Great Falls, MT

Average cloud cover in May - Great Falls, MT
  • Average cloud cover in May: 33

The month with the most cloud cover is February (Cloud cover 46).
The month with the least cloud cover is July (Cloud cover 13).

Average visibility in May
Great Falls, MT

Average visibility in May - Great Falls, MT
  • Average visibility in May: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

Great Falls, Montana, USA

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