May weather forecast
Lewistown, MT

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Weather in May

May signifies a period of increased weather activity with the transition of seasons. With temperatures ascending to 58.5°F (14.7°C), indicating a significant departure from April, the warmth becomes noticeable. A peak rainfall volume of 3.39" (86mm) documents the heaviest downpour for the year. Longer daylight hours coupled with more sunshine manifest the imminent arrival of summer. Following April’s trend, the city witnesses a further decrease of relative humidity.

Temperature

May's arrival coincides with a rise in the average high-temperature, moving from April's frosty 47.8°F (8.8°C) to a refreshing 58.5°F (14.7°C). Throughout the month of May, Lewistown witnesses an average temperature of 40.1°F (4.5°C).

Humidity

In Lewistown, the average relative humidity in May is 65%.

Rainfall

May is the month with the most rainfall. Rain falls for 19.3 days and accumulates 3.39" (86mm) of precipitation.

Snowfall

Months with snowfall are January through June, September through December. In Lewistown, in May, snow falls for 2.4 days, with typically accumulated 2.48" (63mm) of snow. In Lewistown, during the entire year, snow falls for 83.4 days and aggregates up to 45.51" (1156mm) of snow.

Daylight

In May, the average length of the day is 15h and 6min.
On the first day of May, sunrise is at 6:00 am and sunset at 8:29 pm. On the last day of the month, sunrise is at 5:26 am and sunset at 9:04 pm MDT.

Sunshine

In May, the average sunshine is 10h.

UV index

In Lewistown, the average daily maximum UV index in May is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV radiation for the ordinary person.
Note: The UV index of 4 in May translates into these instructions:
Be vigilant - Preventing sunburn is recommended. During midday, the Sun's radiation is strongest, and it's advisable to reduce direct exposure. Consider a wide-brim hat essential for effective sun defense covering your face, neck, and eyes. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.
Updated: Jul 30, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What are the temperatures in May?

In Lewistown, 58.5°F (14.7°C) is the average high-temperature and 40.1°F (4.5°C) is the average low-temperature during May.

What is the average humidity in May?

In Lewistown, the average relative humidity in May is 65%.

What is the rainiest month?

The month with the most rainfall in Lewistown is May, when the rain falls for 19.3 days and typically aggregates up to 3.39" (86mm) of precipitation.

How many days does it rain in May?

In Lewistown, in May, it is raining for 19.3 days, with typically 3.39" (86mm) of accumulated precipitation.

How many days does it snow in May?

In Lewistown, in May, during 2.4 snowfall days, 2.48" (63mm) of snow is typically accumulated.

What is the average length of the day in May?

In Lewistown, the average day length in May is 15h and 6min.

When is the sunrise / sunset in May?

On the first day of May, sunrise is at 6:00 am and sunset at 8:29 pm. On the last day of the month, sunrise is at 5:26 am and sunset at 9:04 pm MDT.

How long on average sun shines in May?

In Lewistown, the average sunshine duration in May is 10h.

What is the UV index reading in May?

In May, the average daily maximum UV index is 4. A UV Index of 3 to 5 symbolizes a moderate health threat from unsafe 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
Lewistown, MT

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

The warmest month (with the highest average high temperature) is July (78.8°F).
The months with the lowest average high temperature are February and December (29.1°F).

  • Average low temperature in May: 40.1°F

The month with the highest average low temperature is August (54.5°F).
The coldest month (with the lowest average low temperature) is February (15.3°F).

Average pressure in May
Lewistown, MT

Average pressure in May - Lewistown, MT
  • Average pressure in May: 29.92"Hg

The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.85"Hg).

Average wind speed in May
Lewistown, MT

Average wind speed in May - Lewistown, MT
  • Average wind speed in May: 8.8mph

The windiest months (with the highest average wind speed) are January, April and October (9.9mph).
The calmest month (with the lowest average wind speed) is August (7.4mph).

Average humidity in May
Lewistown, MT

Average humidity in May - Lewistown, MT
  • Average humidity in May: 65%

The month with the highest relative humidity is February (79%).
The month with the lowest relative humidity is August (47%).

Average rainfall in May
Lewistown, MT

Average rainfall in May - Lewistown, MT
  • Average rainfall in May: 3.39"

The wettest month (with the highest rainfall) is May (3.39").
The driest month (with the least rainfall) is December (0.71").

Average rainfall days in May
Lewistown, MT

Average rainfall days in May - Lewistown, MT
  • Average rainfall days in May: 19.3 days

The month with the highest number of rainy days is May (19.3 days).
The month with the least rainy days is January (5.4 days).

Average snowfall in May
Lewistown, MT

Average snowfall in May - Lewistown, MT
  • Average snowfall in May: 2.48"

The month with the highest snowfall is April (9.13").
The months with the least snowfall are July and August (0").

Average snowfall days in May
Lewistown, MT

Average snowfall days in May - Lewistown, MT
  • Average snowfall days in May: 2.4 days

The month with the highest number of snowfall days is February (15.2 days).
The months with the least snowfall days are July and August (0 days).

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

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

The month with the longest days is June (Average daylight: 15h and 48min).
The month with the shortest days is December (Average daylight: 8h and 36min).

  • Average sunshine in May: 10h and 0min

The month with the most sunshine is July (Average sunshine: 11h and 48min).
The month with the least sunshine is February (Average sunshine: 5h and 30min).

Average sunshine days in May
Lewistown, MT

Average sunshine days in May - Lewistown, MT
  • Average sunshine days in May: 8.9 days

The month with the most sunshine days is September (19.3 days).
The month with the least sunshine days is April (8.3 days).

Average UV index in May
Lewistown, MT

Average UV index in May - Lewistown, 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, April, October, November and December (UV index 2).

Average cloud cover in May
Lewistown, MT

Average cloud cover in May - Lewistown, MT
  • Average cloud cover in May: 36

The month with the most cloud cover is February (Cloud cover 45).
The month with the least cloud cover is July (Cloud cover 16).

Average visibility in May
Lewistown, MT

Average visibility in May - Lewistown, 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).

Lewistown, Montana, USA

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