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Lewis and Clark County (Helena)
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United States weather

Weather in Lewis and Clark County, Montana for May 2026

Your guide to Lewis and Clark County weather in May - trends and predictions

    Temperatures

  • An exceptional deviation from the historical average is forecasted for first days of May 2026 in Lewis and Clark County with the forecasted temperature being 12.8 °F, much lower than usual.

  • In general, the average temperature in Lewis and Clark County at the beginning of May is 16.3 °F. As the month progressed, temperatures tended to significantly warm up, reaching an average of 23.9 °F by the end of May.

    • Rain 🌧️

  • The climate of Lewis and Clark County in May is notably wet, with an average of 12 rainy days, and a total of 71.7 mm of precipitation.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
19
Dry days
Average rainy days
12
Rainy days
Average snowy days
0
Snow days
Average temperatures
18°/4°
Temperatures
Average wind speed
16 km/h
Avg max wind
Average humidity
58 %
Avg humidity

Lewis and Clark County Weather May

Move between months or click on a day
April
June
Sun.Mon.Tue.Wed.Thu.Fri.Sat.
1
Patchy rain possible
15°
2
Patchy rain possible
17°
3
Sunny
23°
4
Overcast
17°
5
Moderate or heavy rain shower
8°
6
Overcast
14°
7
Cloudy
20°
8
Sunny
21°
9
Partly cloudy
24°
10
Moderate rain at times
28°
11
Overcast
24°
12
Patchy rain possible
19°
13
Moderate rain at times
11°
14
Moderate or heavy rain shower
12°
15
Moderate or heavy rain shower
11°
16
Overcast
13°
17
Overcast
16°
18
Patchy rain possible
10°
19
Partly cloudy
14°
20
Patchy rain possible
14°
21
Patchy rain possible
14°
22
Patchy rain possible
15°
23
Patchy rain possible
17°
24
Sunny
18°
25
Sunny
22°
26
Sunny
24°
27
Thundery outbreaks possible
20°
28
Sunny
22°
29
Sunny
27°
30
Sunny
22°
31
Sunny
30°

Temperatures trend during May in Lewis and Clark County

See the weather trend as well as the moving average line

May weather in Lewis and Clark County day by day

Click on a date for more information
April June
Date Weather Temperatures Rain UV More
May 1 Patchy rain possible
Patchy rain possible
 15° /1° 0.1 mm 2
May 2 Patchy rain possible
Patchy rain possible
 17° /3° 0.4 mm 3
May 3 Sunny
Sunny
 23° /3° 0 mm 6
May 4 Overcast
Overcast
 17° /4° 9.8 mm 4
May 5 Moderate or heavy rain shower
Moderate or heavy rain shower
 8° /1° 13.3 mm 2
May 6 Overcast
Overcast
 14° /-1° 0 mm 3
May 7 Cloudy
Cloudy
 20° /0° 0 mm 5
May 8 Sunny
Sunny
 21° /6° 0 mm 6
May 9 Partly cloudy
Partly cloudy
 24° /5° 0 mm 6
May 10 Moderate rain at times
Moderate rain at times
 28° /9° 1.5 mm 6
May 11 Overcast
Overcast
 24° /9° 0 mm 5
May 12 Patchy rain possible
Patchy rain possible
 19° /7° 1.8 mm 4
May 13 Moderate rain at times
Moderate rain at times
 11° /5° 4.5 mm 3
May 14 Moderate or heavy rain shower
Moderate or heavy rain shower
 12° /5° 17.2 mm 3
May 15 Moderate or heavy rain shower
Moderate or heavy rain shower
 11° /4° 11.3 mm 3
May 16 Overcast
Overcast
 13° /2° 0 mm 3
May 17 Overcast
Overcast
 16° /2° 0.5 mm 4
May 18 Patchy rain possible
Patchy rain possible
 10° /6° 3.9 mm 3
May 19 Partly cloudy
Partly cloudy
 14° /1° 0 mm 4
May 20 Patchy rain possible
Patchy rain possible
 14° /2° 0.2 mm 3
May 21 Patchy rain possible
Patchy rain possible
 14° /1° 0.5 mm 3
May 22 Patchy rain possible
Patchy rain possible
 15° /2° 3.3 mm 4
May 23 Patchy rain possible
Patchy rain possible
 17° /3° 3.9 mm 4
May 24 Sunny
Sunny
 18° /4° 0 mm 5
May 25 Sunny
Sunny
 22° /4° 0 mm 6
May 26 Sunny
Sunny
 24° /5° 0 mm 6
May 27 Thundery outbreaks possible
Thundery outbreaks possible
 20° /8° 0 mm 5
May 28 Sunny
Sunny
 22° /8° 0 mm 6
May 29 Sunny
Sunny
 27° /8° 0 mm 7
May 30 Sunny
Sunny
 22° /9° 0 mm 6
May 31 Sunny
Sunny
 30° /9° 0 mm 8
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Important Notice
Our weather forecast for Lewis and Clark County in May is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Lewis and Clark County forecast closer to your planned date for the most up-to-date weather information.
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Lewis and Clark County in May - FAQ

What are the expected maximum and minimum temperatures in Lewis and Clark County during May?

During May, expect a variety of temperatures with highs around 18° and lows near 4°, suitable for diverse activities and preferences.

How much rainfall should be expected in Lewis and Clark County during May?

Moderate rainfall is anticipated in Lewis and Clark County during May, with a total of 71.7 mm spread over approximately 12 days. Considering plans for rainy days is advisable.

What are the typical wind conditions in Lewis and Clark County during May?

The average wind speed in Lewis and Clark County during May is 16 km/h, suggesting breezy to windy conditions, depending on your activities.

May rainfall patterns in Lewis and Clark County

Explore the daily rainfall trends and prepare for Lewis and Clark Countys May weather 💧
Typically, Lewis and Clark County has 12 rainy days in May with a total of 71.7 mm of rainfall.

UV exposure in Lewis and Clark County during May

Stay informed about UV levels for safe outdoor activities throughout the month of May ☀️
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Helena
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Location coordinates Where is Lewis and Clark County?

Get accurate weather forecasts for Lewis and Clark County, located at latitude 46.593 and longitude -112.036. Stay updated with localized weather information tailored for Lewis and Clark County.

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