National Park Service Summer Air temperatures average 75 - 85 F (some days in the 90s) with lows to the 50s. Moderately high humidity. Occasional thunderstorms and dense fog. Water temperatures in summer (May to September) rise from the low 60s to highs in the mid-70s in July. 
Spring and fall Climate is variable. Temperature can drop rapidly after sunset on warm days. Wet suits may be required for river use. 
National Park Service Winter Air temperatures (December to March) are normally below freezing, with frequent snow and ice storms. Water Temperatures drop from the 50s to the 30s by December, with most of the river usually freezing over each winter. Recommended Clothing Always dress in layers in any season. Be prepared for rain and cold weather at any time. Hypothermia is possible, especially on the river, even during the summer. Boaters and anglers should be prepared for cold water and always wear a properly fitted life jacket. |
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Last updated: January 13, 2015