Climate and monthly weather forecast
Idaho, USA

Flag of Idaho, USA
Flag of Idaho, USA

The climate of Idaho

Idaho has diverse climate types, with a predominantly continental flavor in the central and eastern regions (Köppen climate classification Dsa, Dsb). The western portion has a maritime influence (Köppen Cfb, Csb) from the Pacific Ocean. Idaho lies in the Pacific Northwest region of the United States. The state borders with Montana and Wyoming in the east, Utah, and Nevada in the south, Oregon and Washington in the west, and the Canadian province of British Columbia in the north. The variation in topography, altitude, geography, and proximity to the Pacific Ocean influences the climate.

Idaho, the Gem State, is home to rugged mountain ranges, grassy valleys, arid plains, and fertile lowlands. The average elevation is 1520 meters above sea level, with the highest point at 3859 meters at Borah Peak. The landscape is rugged, and the state has one of the largest natural areas in the United States. The Sawtooth Range is prominent, while others such as the Bitterroot Range, White Cloud Mountains, Clearwater Mountains, and stretches of the Rocky Mountains constitute the chiefly mountainous regions. The principal rivers are Snake, Clearwater, and Salmon, while the Snake River Plain in the south has fertile agricultural land. The panhandle and areas north of the Salmon River follow the Pacific Time Zone, while the south lies in the Mountain Time Zone.

The Pacific Ocean exerts a maritime influence in the north and west of Idaho, which results in cloudy, humid, and wet winters. The eastern part is free of the oceanic influence and exhibits the reverse pattern of wet summers and dry winters. Temperatures above 100°F (37.8°C) are rare in the summer. Summers have the highest difference between day and night temperatures that sees cooler nights even when days are hot. Winters are cold, but temperatures below 0°F (-17.8°C) are rare for extended periods. Fog is a regular feature in the cold season. Spring and autumn have comfortable temperatures in the majority of the state.

The average annual precipitation ranges from 10" (254mm) in the arid southwest regions, much of the Snake River and Central Plains to 50" (1270mm) at higher elevations and Clearwater, Payette, and Boise river basins. The north and west see the wettest period during the winter, while the east receives the majority of rainfall in the summer. Snowfall is abundant in the high mountains, with the annual total in Shoshone County at 500" (12700mm). Mullan Pass, which recorded the greatest snow depth of 182" (4623mm) on February 20, 1954, has a long-term seasonal average of 182" (4623mm) of snowfall in the winter. The average annual sunshine lasts for 2700 hours in Idaho.

Orofino recorded the highest temperature of 118°F (47.8°C) on July 28, 1934, in Idaho, while Island Park Dam recorded the lowest temperature of -60°F (-51.1°C) on January 18, 1943.

The best time to visit Idaho

The best time to visit Idaho is from mid-April to late October during the spring, summer, and fall seasons. Early spring is cold and often sees snow and ice in the highlands. The melting of snow begins by April and is the period of watching migratory birds on the lakes and rivers. Summer is warm to hot, with many sunny days, even during the period of high precipitation. Summers tend to be cool in the high mountain ranges and witness a large number of visitors. Early autumn has one of the best conditions with sunny days, a colorful landscape, and breezy evenings.

The worst time to visit Idaho

The worst time to visit Idaho, if any, is from December to February when the highlands are under cover of snow and ice. Cold fronts occasionally occur but rarely last more than a week, and temperatures below 0°F (-17.8°C) are rare. Fog is one of the challenges during the winter when the visibility limits to less than one-fourth of a mile. Mountain trails face closures during heavy snowfall, while roads become slippery in icy conditions. Many areas register between 20" (508mm) to 60" (1524mm) of snowfall in the winter season. Contrary to expectations, winter sees a fair number of tourists in Idaho.

Weather hazards

Idaho is prone to thunderstorms and flooding in late spring and early summer. Strong winds accompany thunderstorms, which often bring heavy rain and cause lightning strikes. Windstorms are common during the summer and cause damage to trees and communication lines. Hot conditions during the peak summer and lightning during thunderstorms create the danger of wildfires in the forested areas. Snowstorms frequently hound the high mountain slopes in the winter and deposit vast amounts of snow. Hailstorms occasionally damage crops during spring as well as summer, but the size of hail rarely extends half an inch in diameter.

Weather in January

January is the coldest month of the year in Idaho, with temperatures in the frigid zone. The average low temperatures are in the icy -2°F (-18.9°C) to 22°F (-5.6°C) range, while the average high temperatures are in the cold zone of 26°F (-3.3°C) to 43°F (6.1°C). Weather in January »

Weather in February

February is icy in the winter of Idaho, with cloudy skies, and wetter north and west regions. The average temperatures range from 33°F (0.6°C) to 50°F (10°C) in the day and -1°F (-18.3°C) to 30°F (-1.1°C) during the night. Weather in February »

Weather in March

March is cold at the beginning of the spring season in Idaho, with the average low temperatures in the freezing 10°F (-12.2°C) to 37°F (2.8°C) range. The days are in the mild zone of 41°F (5°C) to 60°F (15.6°C) across the state with a moderate amount of precipitation. Snowfall of 5" (127mm) to 10" (254mm) occurs in the northern highlands as the skiing season continues in the rising temperatures. Weather in March »

Weather in April

April welcomes bright days to Idaho, with a significant decrease in rain and snow. The precipitation ranges from 1" (25mm) to 3" (76mm), and the snow season is over in the south. The icy cold gives way to bearable temperatures that average between 19°F (-7.2°C) to 43°F (6.1°C) during the nights. Weather in April »

Weather in May

May is a beautiful time to visit Idaho with comfortable temperatures and plenty of sunshine. The spring blossoms with green contours all over the state. Pocatello in the east has comfortable temperatures in the 40°F (4.4°C) to 67°F (19.4°C) range, while salmon registers between 41°F (5°C) to 67°F (19.4°C). Weather in May »

Weather in June

June has the longest days of the year in Idaho as the state basks in glorious sunshine. The average high temperatures are in the warm 69°F (20.6°C) to 86°F (30°C) range, while the average low temperatures are in the mild zone of 42°F (5.6°C) to 57°F (13.9°C). Weather in June »

Weather in July

July is the hottest month of the year in Idaho, with average high temperatures in the warm zone of 79°F (26.1°C) to 95°F (35°C). Nights are comfortable in the range of 36°F (2.2°C) to 60°F (15.6°C), with a decrease in humidity compared to the day. Weather in July »

Weather in August

August is warm to hot in the summer of Idaho, with mostly clear skies. Days register in the warm to hot zone of 79°F (26.1°C) to 94°F (34.4°C), while nights are comfortable between 33°F (0.6°C) to 59°F (15°C). Little precipitation occurs in the north and east, but windstorms and forest fires are a threat to the tree-covered mountain slopes. Weather in August »

Weather in September

September sees a transition to the beautiful autumn season in Idaho, with average high temperatures in the 69°F (20.6°C) to 83°F (28.3°C) range. The nights are on the colder side in the average zone of 26°F (-3.3°C) to 43°F (6.1°C) and even freezing in the hills. Weather in September »

Weather in October

October is warm to cold in the fall season of Idaho and full of brilliant colors. The average high temperatures are in the range of 55°F (12.8°C) to 70°F (21.1°C), while the average low temperatures are between 26°F (-3.3°C) to 45°F (7.2°C) statewide. Fall colors are at their peak by mid-October, and the refreshing air, scenic wilderness, and abundant wildlife make the conditions lively. Weather in October »

Weather in November

November ends the autumn season in Idaho, with cold temperatures in the average range of 11°F (-11.7°C) to 53°F (11.7°C) across the state. Coeur d'Alene in the north experiences freezing nights with temperatures between 32°F (0°C) to 44°F (6.7°C), while Boise in the southwest has mild days between 32°F (0°C) to 48°F (8.9°C). The precipitation picks up to register 3" (76mm) to 5" (127mm) in the north, but the east is relatively dry between 1" (25mm) to 2" (51mm). Weather in November »

Weather in December

December is bitterly cold in Idaho with the average high temperatures in the 27°F (-2.8°C) to 42°F (5.6°C) range and the average low temperatures in the freezing zone of -2°F (-18.9°C) to 28°F (-2.2°C). The eastern parts of the state, such as Preston, are regularly below freezing and register between 15°F (-9.4°C) to 32°F (0°C). The north and central parts are snowier than the rest of the regions and receive between 5" (127mm) to 15" (381mm). Weather in December »


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