May weather forecast and climate
Boulder, MT

Weather in May

The last month of the spring, May, is a moderate month in Boulder, Montana, with average temperature fluctuating between 35.2°F (1.8°C) and 58.5°F (14.7°C).

Temperature

In May, the average high-temperature increases, from a frosty 46.4°F (8°C) in April, to a moderate 58.5°F (14.7°C). The average low-temperature, in Boulder, is 35.2°F (1.8°C).

Humidity

In May, the average relative humidity in Boulder is 64%.

Rainfall

In Boulder, during May, the rain falls for 18.2 days and regularly aggregates up to 2.36" (60mm) of precipitation. Throughout the year, there are 133.7 rainfall days, and 16.38" (416mm) of precipitation is accumulated.

Snowfall

Months with snowfall are January through June, September through December. In Boulder, during 4.4 snowfall days, 2.64" (67mm) of snow is typically accumulated. In Boulder, during the entire year, snow falls for 105.8 days, and aggregates up to 55.12" (1400mm) of snow.

Daylight

The average length of the day in Boulder is 15h.

Sunshine

In Boulder, the average sunshine is 10.2h.

UV index

The average daily maximum UV index in May is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV rays for the average person.
Note: The average daily UV index of 4 transform into the following instructions:
Take precautions - Protection against sunburn is recommended. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.
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FAQ

What is the average humidity in May in Boulder?

The average relative humidity in May in Boulder, Montana, is 64%.

How many days does it rain in May in Boulder?

In Boulder, Montana, in May, during 18.2 rainfall days, 2.36" (60mm) of precipitation is typically accumulated.

How much does it snow in Boulder in May?

In Boulder, during May, snow falls for 4.4 days and regularly aggregates up to 2.64" (67mm) of snow.

What is the average length of the day in May in Boulder?

The average length of the day in May in Boulder is 15h.

How long on average sun shines in May in Boulder?

In Boulder, Montana, the average sunshine in May is 10.2h.

What is the UV index intensity in May in Boulder?

The average daily maximum UV index in May in Boulder is 4. A UV Index reading of 3 to 5 represents a moderate health threat from unsafe exposure to the Sun's UV rays.

Average temperature in May
Boulder, MT

Average temperature in May - Boulder, MT
  • Average high temperature in May: 58.5°F

The warmest month (with the highest average high temperature) is July (79.7°F).
The month with the lowest average high temperature is December (27°F).

  • Average low temperature in May: 35.2°F

The month with the highest average low temperature is August (48.6°F).
The coldest month (with the lowest average low temperature) is December (12.6°F).

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Average pressure in May
Boulder, MT

Average pressure in May - Boulder, MT
  • Average pressure in May: 29.95"

The month with the highest atmospheric pressure is January (30.19").
The month with the lowest atmospheric pressure is June (29.91").

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Average wind speed in May
Boulder, MT

Average wind speed in May - Boulder, MT
  • Average wind speed in May: 5.4mph

The windiest months (with the highest average wind speed) are January and November (6.5mph).
The calmest month (with the lowest average wind speed) is August (4.7mph).

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Average humidity in May
Boulder, MT

Average humidity in May - Boulder, MT
  • Average humidity in May: 64%

The month with the highest relative humidity is January (86%).
The month with the lowest relative humidity is August (46%).

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Average rainfall in May
Boulder, MT

Average rainfall in May - Boulder, MT
  • Average rainfall in May: 2.36"

The wettest month (with the highest rainfall) is June (2.68").
The driest month (with the least rainfall) is December (0.79").

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Average rainfall days in May
Boulder, MT

Average rainfall days in May - Boulder, MT
  • Average rainfall days in May: 18.2 days

The month with the highest number of rainy days is May (18.2 days).
The month with the least rainy days is November (7.5 days).

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Average snowfall in May
Boulder, MT

Average snowfall in May - Boulder, MT
  • Average snowfall in May: 2.64"

The month with the highest snowfall is February (9.72").
Months with the least snowfall are July and August (0").

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Average snowfall days in May
Boulder, MT

Average snowfall days in May - Boulder, MT
  • Average snowfall days in May: 4.4 days

The month with the highest number of snowfall days is February (18 days).
Months with the least snowfall days are July and August (0 days).

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Average daylight in May /
Average sunshine in May
Boulder, MT

Average daylight in May / Average sunshine in May - Boulder, MT
  • Average daylight in May: 15h

The month with the longest days is June (Average daylight: 15.7h).
The month with the shortest days is December (Average daylight: 8.7h).

  • Average sunshine in May: 10.2h

The month with the most sunshine is July (Average sunshine: 11.7h).
Months with the least sunshine are January and December (Average sunshine: 5.6).

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Average sunshine days in May
Boulder, MT

Average sunshine days in May - Boulder, MT
  • Average sunshine days in May: 9.3 days

The month with the most sunshine days is September (17.9 days).
The month with the least sunshine days is February (8.5 days).

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Average UV index in May
Boulder, MT

Average UV index in May - Boulder, MT
  • Average UV index in May: 4

The month with the highest UV index is July (UV index 6).
The month with the lowest UV index is February (UV index 1).

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Average cloud cover in May
Boulder, MT

Average cloud cover in May - Boulder, MT
  • Average cloud cover in May: 34

The month with the most cloud cover is February (Cloud cover 48).
The month with the least cloud cover is August (Cloud cover 15).

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Average visibility in May
Boulder, MT

Average visibility in May - Boulder, MT
  • Average visibility in May: 6mi

Months with the highest visibility are April, May, June, July, August, September, October and November (6mi).
Months with the lowest visibility are January, February, March and December (5mi).

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