Climate and Average Weather Year Round in Helena Valley Southeast United States

In Helena Valley Southeast, the summers are short, warm, and mostly clear and the winters are freezing, snowy, and partly cloudy. Over the course of the year, the temperature typically varies from 14°F to 87°F and is rarely below -6°F or above 96°F.

Based on the tourism score, the best time of year to visit Helena Valley Southeast for warm-weather activities is from early July to mid August.

The hot season lasts for 2.8 months, from June 15 to September 9, with an average daily high temperature above 75°F. The hottest month of the year in Helena Valley Southeast is July, with an average high of 85°F and low of 56°F.

The cold season lasts for 3.3 months, from November 17 to February 25, with an average daily high temperature below 42°F. The coldest month of the year in Helena Valley Southeast is December, with an average low of 16°F and high of 33°F.

In Helena Valley Southeast, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year in Helena Valley Southeast begins around June 15 and lasts for 3.7 months, ending around October 6.

The clearest month of the year in Helena Valley Southeast is July, during which on average the sky is clear, mostly clear, or partly cloudy 74% of the time.

The cloudier part of the year begins around October 6 and lasts for 8.3 months, ending around June 15.

The cloudiest month of the year in Helena Valley Southeast is March, during which on average the sky is overcast or mostly cloudy 63% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Helena Valley Southeast varies throughout the year.

The wetter season lasts 2.3 months, from April 27 to July 3, with a greater than 21% chance of a given day being a wet day. The month with the most wet days in Helena Valley Southeast is June, with an average of 9.1 days with at least 0.04 inches of precipitation.

The drier season lasts 9.8 months, from July 3 to April 27. The month with the fewest wet days in Helena Valley Southeast is February, with an average of 2.5 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation in Helena Valley Southeast changes throughout the year.

Rain alone is the most common for 9.4 months, from February 21 to December 3. The month with the most days of rain alone in Helena Valley Southeast is June, with an average of 9.1 days.

Snow alone is the most common for 2.6 months, from December 3 to February 21. The month with the most days of snow alone in Helena Valley Southeast is December, with an average of 1.6 days.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Helena Valley Southeast experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 7.2 months, from March 21 to October 28, with a sliding 31-day rainfall of at least 0.5 inches. The month with the most rain in Helena Valley Southeast is June, with an average rainfall of 2.1 inches.

The rainless period of the year lasts for 4.8 months, from October 28 to March 21. The month with the least rain in Helena Valley Southeast is January, with an average rainfall of 0.2 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Helena Valley Southeast experiences some seasonal variation in monthly snowfall.

The snowy period of the year lasts for 5.4 months, from October 29 to April 12, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Helena Valley Southeast is December, with an average snowfall of 2.6 inches.

The snowless period of the year lasts for 6.5 months, from April 12 to October 29. The least snow falls around July 24, with an average total accumulation of 0.0 inches.

The length of the day in Helena Valley Southeast varies significantly over the course of the year. In 2024, the shortest day is December 21, with 8 hours, 34 minutes of daylight; the longest day is June 20, with 15 hours, 51 minutes of daylight.

The earliest sunrise is at 5:33 AM on June 15, and the latest sunrise is 2 hours, 38 minutes later at 8:12 AM on January 2. The earliest sunset is at 4:39 PM on December 9, and the latest sunset is 4 hours, 45 minutes later at 9:25 PM on June 25.

Daylight saving time (DST) is observed in Helena Valley Southeast during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level in Helena Valley Southeast, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Helena Valley Southeast experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 7.2 months, from October 6 to May 13, with average wind speeds of more than 6.4 miles per hour. The windiest month of the year in Helena Valley Southeast is January, with an average hourly wind speed of 7.6 miles per hour.

The calmer time of year lasts for 4.8 months, from May 13 to October 6. The calmest month of the year in Helena Valley Southeast is August, with an average hourly wind speed of 5.3 miles per hour.

The predominant average hourly wind direction in Helena Valley Southeast is from the west throughout the year.

To characterize how pleasant the weather is in Helena Valley Southeast throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Helena Valley Southeast for general outdoor tourist activities is from early July to mid August, with a peak score in the last week of July.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Helena Valley Southeast for hot-weather activities is from early July to early August, with a peak score in the last week of July.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Helena Valley Southeast typically lasts for 4.7 months (144 days), from around May 7 to around September 28, rarely starting before April 19 or after May 28, and rarely ending before September 8 or after October 17.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms in Helena Valley Southeast should appear around April 26, only rarely appearing before April 13 or after May 9.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.1 months, from May 16 to August 20, with an average daily incident shortwave energy per square meter above 6.4 kWh. The brightest month of the year in Helena Valley Southeast is July, with an average of 7.5 kWh.

The darker period of the year lasts for 3.5 months, from October 28 to February 13, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest month of the year in Helena Valley Southeast is December, with an average of 1.4 kWh.

For the purposes of this report, the geographical coordinates of Helena Valley Southeast are 46.615 deg latitude, -111.922 deg longitude, and 3,799 ft elevation.

The topography within 2 miles of Helena Valley Southeast contains only modest variations in elevation, with a maximum elevation change of 190 feet and an average elevation above sea level of 3,799 feet. Within 10 miles contains only modest variations in elevation (3,225 feet). Within 50 miles contains large variations in elevation (6,155 feet).

The area within 2 miles of Helena Valley Southeast is covered by grassland (75%) and cropland (16%), within 10 miles by grassland (33%) and shrubs (32%), and within 50 miles by grassland (30%) and trees (27%).