Montana, the fourth-largest US state in land area, has large climatic variations due to its geographic diversity and altitudinal range. Elevations across the state range from about 1,800 to 12,800 feet, leading to large variations in temperature. The central and eastern portions of the state are part of the Northern Great Plains and experience warm summers and cold winters. The western part of the state is mountainous, with snowy winters and cool summers. Average winter low temperatures range from less than 5°F in the northeastern corner of the state to around 20°F in south-central Montana and western mountain valleys (1991–2020 averages). Typical summer high temperatures range from the low 70s (°F) to the high 80s across the state, with cooler temperatures at high elevations. Montana’s topographic variability causes large regional variations in precipitation, with annual totals ranging from 15 inches or less across most of central and eastern Montana to more than 45 inches in some mountainous locations in the northwest. Most of the state’s precipitation falls during the summer months, although some high-elevation regions experience a peak during the winter and spring months due to abundant snowfall induced by orographic enhancement (the increase of precipitation with elevation on the upwind side of mountain ranges). Annual snowfall varies across the state, with some areas at high elevations receiving more than 300 inches.
Time series of observed and projected temperature change (in degrees Fahrenheit) for Montana from 1900 to 2100 as described in the caption.
Y-axis values range from negative 6 to positive 20 degrees. Observed annual temperatures from 1900 to 2024 show variability and range from negative 3.7 to positive 4.0 degrees. By the end of the century, projected increases in temperature range from 1.3 to 8.3 degrees under the lower emissions pathway, from 4.2 to 11.3 degrees under the intermediate pathway, and from 8.7 to 18.0 degrees under the higher pathway.
Annual average temperatures in Montana have increased more than 2.5°F since the beginning of the 20th century, higher than the warming for the contiguous United States as a whole (Figure 1). The first 25 years of this century represent the warmest period on record for Montana. Temperatures have increased in all seasons, with the largest increases seen in winter and fall temperatures. Since the 1980s, winter temperatures have mostly been above average (Figure 2a). Summer temperatures have generally been near or above average since the late 1990s, with the 2020–2024 period having the highest 5-year average, surpassing the previous highs of the 1930s (Figure 2b). The number of very hot days is highly variable and shows no long-term trend; the highest 5-year averages were recorded during the extreme summer heat of the 1930s Dust Bowl era (Figure 3a). Montana rarely experiences very high nighttime temperatures due to its dry air and high average elevation; however, the 5-year averages for nights with a minimum temperature of 60°F or higher have been near or above average since the late 1990s but still below the highs of the 1930s (Figure 3b). The number of very cold days varies from year to year; 5-year values were mostly below average for most of the 2000s, but the 2020–2024 period was slightly above average (Figure 4).
Two graphs of the observed (a) winter and (b) summer average temperatures for Montana from 1895–96 to 2023–24 and 1895 to 2024, respectively, as described in the caption.
Panel A: Winter Average Temperature
Y-axis values range from 8 to 32 degrees Fahrenheit. Annual values show year-to-year variability and range from 9.3 to 29.1 degrees. Five-year values also show variability and are mostly below the long-term average of 20.1 degrees between 1895 and 1979 but are all above average since 1980. The 1915 to 1919 and 1935 to 1939 periods have the lowest 5-year values at 16.3 and 16.9 degrees, respectively, and the 2000 to 2004, 2005 to 2009, and 2020 to 2024 periods have the highest at 23.1, 22.9, and 23.1 degrees, respectively.
Panel B: Summer Average TemperatureY-axis values range from 56 to 70 degrees Fahrenheit. Annual values show year-to-year variability and range from 57.6 to 67.7 degrees. Five-year values also show variability and are all near or below the long-term average of 62.9 degrees between 1895 and 1929, all above average between 1930 and 1939, and mostly below average between 1940 and 1994. Since 1995, 5-year values are all above average. The 1905 to 1909 and 1950 to 1954 periods have the lowest 5-year values at 61.3 and 61.2 degrees, respectively, and the 1930 to 1934 and 2020 to 2024 periods have the highest at 64.8 and 65.4 degrees, respectively.
Two graphs of the observed annual number of (a) very hot days and (b) warm nights for Montana from 1900 to 2024 as described in the caption.
Panel A: Very Hot Days
Y-axis values range from 0 to 20 days. Annual values show year-to-year variability and range from 0.4 to 18.9 days. Five-year values also show variability and are mostly near or below the long-term average of 6.2 days across the entire period, showing no clear trend. Exceptions include the 1930 to 1934, 1935 to 1939, and 2000 to 2004 periods, which have the highest 5-year values at 11.3, 9.8, and 9.5 days, respectively. The 1975 to 1979 period has the lowest 5-year value at 3.5 days.
Panel B: Warm NightsY-axis values range from 0 to 32 nights. Annual values show year-to-year variability and range from 1.7 to 28.4 nights. Five-year values also show variability and are all below the long-term average of 9.1 nights between 1900 and 1914, all above average between 1915 and 1939 except for the 1925 to 1929 period, and all near or below average between 1940 and 1979. Since 1980, 5-year values are all near or above average except for the 1990 to 1994 period. The 1900 to 1904 period has the lowest 5-year value at 5.0 nights, and the 1930 to 1934 and 1935 to 1939 periods have the highest at 13.0 and 14.3 nights, respectively.
Graph of the observed annual number of very cold days for Montana from 1900 to 2024 as described in the caption.
Y-axis values range from 0 to 14 days. Annual values show year-to-year variability and range from 0 to 12.9 days. Five-year values also show variability and are below the long-term average of 3.3 days for the 1900 to 1904 period, mostly above average between 1905 and 1939, all below average between 1940 and 1964 except for the 1950 to 1954 period, and all near or above average between 1965 and 1984. Between 1985 and 2019, all 5-year values are near or below average; however, the 2020 to 2024 period is above average. The 2000 to 2004 period has the lowest 5-year value at 1.3 days, and the 1915 to 1919 and 1935 to 1939 periods have the highest at 6.4 and 6.0 days, respectively.
Statewide total annual precipitation has varied from a low of 12.6 inches in 1931 to a high of 26.2 inches in 1927 (Figure 5). There is no clear long-term trend in annual precipitation. The number of 1-inch extreme precipitation events has generally been near or above average since the late 1960s (Figure 6).
Graph of the observed total annual precipitation for Montana from 1895 to 2024 as described in the caption.
Y-axis values range from 10 to 28 inches. Annual values show year-to-year variability and range from 12.6 to 26.1 inches. Five-year values also show variability, with no clear trend, and are mostly near or above the long-term average of 18.7 inches across the entire period. Exceptions include the 1930 to 1934, 1935 to 1939, and 2000 to 2004 periods, which have the lowest 5-year values at 16.4, 15.9, and 16.4 inches, respectively. The 1895 to 1899, 1905 to 1909, and 2010 to 2014 periods have the highest 5-year values at 20.4, 20.5, and 20.7 inches, respectively.
Graph of the observed annual number of 1-inch extreme precipitation events for Montana from 1900 to 2024 as described in the caption.
Y-axis values range from 0.0 to 3.5 events. Annual values show year-to-year variability and range from 0.5 to 3.1 events. Five-year values also show variability and are mostly below the long-term average of about 1.5 events between 1915 and 1964. One exception is the 1940 to 1944 period, which has the highest 5-year value at 1.99 events. Since 1965, 5-year values are mostly near or above average. The 1945 to 1949 period has the lowest 5-year value at 1.2 events.
Montana serves as a major water source for other states, and changes in precipitation can have broad impacts beyond its boundaries. Montana is one of the few areas of the globe whose water feeds three oceans: the Missouri River system flows in the Atlantic Ocean; the Belly, Saint Mary, and Waterton Rivers circulate into the Arctic Ocean via Hudson Bay; and the Columbia River system runs into the Pacific Ocean. Streamflow in these rivers relies on meltwater from the snowpack in the late spring and summer. Some of the higher mountain locations, such as Noisy Basin, typically record a late-season snow water equivalent (the amount of water contained within the snowpack) of around 40 inches (Figure 7). In 2024, Montana had its lowest statewide snowpack in 25 years, posing a threat to downstream water supplies.
Time series of the annual variations in the April 1 snow water equivalent at Noisy Basin, Montana, from 1975 to 2024 as described in the caption.
Y-axis values range from 0 to 80 inches. Annual values show year-to-year variability and range from a low of 24.5 inches in 2001 to a high of 72.2 inches in 1997. Annual values are mostly between 30 and 50 inches across the entire period. The highest values at more than 50 inches occurred in 1997, 2011, and 2018, and the lowest values at less than 30 inches occurred in 1988, 1994, and 2001.
Extreme precipitation events during the spring thaw can cause severe flooding. In 1964, a cool spring delayed melting of the snowpack. From June 8 to 9, heavy rains fell on the above-average snowpack, with some areas receiving more than 10 inches in 36 hours. This caused one of the worst flash floods in the state’s history, with at least 28 deaths and damages of more than $50 million. In 2011, heavy spring rains, along with an extremely heavy snowpack, caused significant flooding across the state. Multiple stations reported more than 10 inches of rain during the month of May, making it the second-wettest May in Montana’s history, with many rivers hitting record levels. Below-normal temperatures in the area caused floating ice to accumulate in some streams and rivers, leading to ice jams that obstructed streamflow and resulted in additional flooding. By mid-June, 31 of the state’s 56 counties and 4 of the state’s 7 reservations were declared disaster areas. Total damages across the state were estimated at more than $50 million. Ice jam flooding can also occur during rapid spring warming.
As an agriculturally dependent state, Montana is particularly vulnerable to drought. The Dust Bowl is by far the most famous drought of the past 100 years, but recent severe droughts are also noteworthy. In 2012, the state experienced the driest July–September period in the historical record (1895–2024). By October 2012, much of the southern half of the state was in severe drought (as defined by the US Drought Monitor). The drought provided ideal conditions f or wildfires, and more than 2,000 fires burned over 1.2 million acres. Nearly all of Montana experienced drought classified as severe or worse in 2021 and 2022. These conditions contributed to a destructive wildfire season in 2021, when nearly 750,000 acres burned across the state. The state is also susceptible to flash drought (the rapid onset or intensification of drought). During the 2017 summer, a severe flash drought destroyed livestock and reduced agricultural production.
During the summer months, the state experiences frequent thunderstorms, which can produce hail, lightning, and strong winds. Tornadoes are infrequent and occur mostly in the eastern third of the state. In June 2016, an EF3 tornado struck Baker (near the North Dakota border), destroying two homes, damaging more than 40 structures, and injuring seven people. In July 2024, strong winds (80–100 mph) from a rare derecho (a widespread, long-lived straight-line windstorm associated with a series of severe thunderstorms) brought extensive damage to west-central Montana, snapping power poles, damaging hundreds of homes, and destroying more than 1,000 trees in the city of Missoula alone.
Montana’s northern location makes the state highly susceptible to cold Arctic air and winter storm systems, including heavy snows, high winds, and low wind chill temperatures. Due to the lack of mountain barriers to the north, blizzards are most common in the northeastern part of the state, and areas east of the Rockies can experience bitterly cold temperatures, occasionally lower than −30°F. The state set a record low of −70°F at Rogers Pass in 1954, the lowest minimum temperature ever observed in the contiguous US. Alternatively, the state is prone to summer hot spells, with a record high of 117°F observed on two occasions—at Medicine Lake in 1937 and at Glendive in 1893. This maximum-temperature record exceeds those of several states in the Southeast and is a result of the dry air and downslope winds in the lower elevations of Montana’s eastern plains. Chinook winds—warm and dry rapidly descending winds that occur along the eastern slopes of the Rocky Mountains—are common during the winter months and often bring large and sudden temperature swings. Over January 14–15, 1972, chinook winds caused the temperature in Loma to increase from −54°F to 49°F (a 103°F change), the largest 24-hour temperature change in US history. Although these winds can bring pleasant higher temperatures during the winter months, they can be accompanied by strong gusts and very dry conditions, resulting in potential property damage, quickly melting snow cover, and increased wildfire risk.
Under the intermediate and higher emissions pathways, historically unprecedented warming is projected during this century (Figure 1). Even under the lower emissions pathway, some projections show annual average temperatures exceeding historical record levels by the middle of the century. However, projections for all three pathways show a large range of potential temperature increases, and some projections for the lower pathway are comparable to recent observed values. Increases in heat wave intensity are projected, but the intensity of cold waves is projected to decrease.
Rising temperatures are expected raise the snow line (the average lowest elevation at which snow falls) and increase the likelihood that precipitation falls as rain instead of snow. This would reduce water storage in the snowpack, particularly at those lower mountain elevations that are now on the margins of reliable snowpack accumulation. Higher spring temperatures are also expected to result in earlier melting of the snowpack, further decreasing water availability during the summer months. Changes in snowmelt patterns could also affect water-reliant industries, such as mining and tourism.
Under the intermediate emissions pathway, statistically significant increases in total spring precipitation are projected by midcentury across most of Montana but are less certain elsewhere (Figure 8). Increased spring precipitation can have both positive and negative impacts on Montana’s agricultural economy, improving soil moisture but potentially delaying planting and resulting in yield losses. Statistically significant increases are also projected in total annual precipitation and winter precipitation across southern portions of the state. There is uncertainty in projections for summer and fall precipitation.
Extreme precipitation events are projected to become more frequent. The combination of more extreme precipitation events and more winter and spring precipitation falling as rain rather than snow is expected to increase the risk of flooding.
Map of the contiguous United States showing the projected changes in total spring precipitation by the middle of this century as described in the caption. The state of Montana is outlined in black.
Legend values range from less than negative 10 to greater than positive 15 percent. Note: unless otherwise specified, projected values are not statistically significant.
Montana
Nearly all of Montana is projected to see statistically significant increases in total precipitation of 10 to 15 percent.
Contiguous USProjected increases in total spring precipitation are as follows: up to 5 percent across a narrow strip running westward and curving northwestward from western Georgia into the Pacific Northwest; 5 to 10 percent in the Southeast, Mid-Atlantic, and Northeast, as well as southern areas of the Midwest, central portions of the Great Plains, and portions of the Northwest; and 10 to 15 percent in the northern areas of the Northeast, Midwest, and Great Plains, with statistically significant increases in the 10 to 15 percent range across the northern border of the country stretching from Maine to Montana.
Decreases of up to 10 percent are seen across the southern Great Plains and Southwest, including southern Texas, all of Arizona, and most of New Mexico and California.
Higher temperatures are expected to increase evaporation rates and decrease soil moisture, leading to more intense future droughts and, potentially, to increases in the frequency and severity of wildfires.
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