Idaho Climate Guide: Five Distinct Regions

Idaho's climate defies summary. From rainforests to deserts, alpine tundra to temperate valleys, the state spans five Köppen zones across 300+ miles of latitude and 10,000 ft of elevation.

1. Northern Idaho (Panhandle) – Temperate Continental / Marine Transition

• Key Towns: Coeur d'Alene, Sandpoint, Bonners Ferry, Priest River
• Winter: Cold, snowy (20–30°F avg low; 50–70" snow)
• Summer: Warm, moderate (75–85°F high; low humidity)
• Precip: 25–45" – winter max, summer dry
• Growing Season: 120–150 days

2. North Central (Palouse) – Continental Mediterranean

• Key Towns: Moscow, Lewiston, Grangeville
• Winter: Cold, moderate snow (20–30°F; 20–40")
• Summer: Hot, dry (85–95°F; <1" rain Jul–Sep)
• Precip: 20–25" – winter/spring max
• Special: Lewiston (730 ft) = "Banana Belt" – earliest spring, hottest summers

3. Central Mountains – Highland Continental / Subalpine

• Key Towns: McCall, Stanley, Sun Valley/Ketchum, Driggs, Island Park
• Winter: Severe, deep snow (0–20°F; 150–300"+)
• Summer: Mild days, cold nights (70–80°F / 35–45°F)
• Precip: 25–40" – snow dominant
• Frost: Possible any month (Stanley = "Nation's Coldest" frequent winner)

4. Southwest (Treasure Valley) – Semi-Arid / Cold Desert

• Key Towns: Boise, Nampa, Meridian, Caldwell, Mountain Home
• Winter: Mild-cold, little snow (25–35°F; 15–25")
• Summer: Hot, very dry (90–100°F; <0.5" rain Jul–Sep)
• Precip: 11–13" – winter/spring
• Growing: 180+ days – Idaho's ag heartland (irrigated)

5. Southeast (Upper Snake / High Desert) – Cold Semi-Arid

• Key Towns: Idaho Falls, Pocatello, Rexburg, Blackfoot, Twin Falls
• Winter: Cold, snowy (10–25°F; 30–60")
• Summer: Warm, low humidity (80–90°F)
• Precip: 10–15" – winter/spring peak
• Wind: Persistent SW flow – affects irrigation, drying

Microclimate Masters

• Inversions: Treasure Valley traps cold/fog/pollution (Dec–Jan)
• Rain Shadows: Lewiston (wet) vs. Pullman (dry) – 20 mi, 2× precip
• Cold Air Drainage: Stanley, Driggs, Island Park – frost pockets
• Lake Effect: Lake Pend Oreille → Sandpoint snow belts

Climate Change Signal

• +2–3°F since 1900; nights warming faster
• Snowpack peak earlier, melt faster; rain-on-snow ↑
• Fire season +40 days since 1980
• Growing zones shifted ~½ zone north

Idaho climate = elevation + latitude + Pacific moisture access. Check your specific valley.