Grand Isle County Climate
Grand Isle County, Vermont
Avg Annual Temp
46.7°F
Annual Precip
35.0"
Annual Snowfall
50.1"
Extreme Heat Days
6.4
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Grand Isle County Weather
Vermont’s Unique Lake Climate
Grand Isle averages 46.7°F, which is warm for Vermont but still 7 degrees below the national median. Its island geography creates a unique microclimate in Lake Champlain.
Second Warmest in Vermont
The county is 3.1 degrees warmer than the state average, ranking as the second warmest in this data set. The lake water acts as a thermal battery, softening winter's edge.
Drier and Warmer Than Most
Grand Isle's 46.7°F average is much higher than Franklin’s 44.5°F. It is also the driest county in the group, receiving only 35.0 inches of annual precipitation.
Less Snow and Warmer Summers
The county receives only 50.1 inches of snow, the lowest in this group by far. Summers are warm and humid, with July averaging 71.7°F and 6 days of extreme heat.
Focus on Wind and Heat
Lakeside winds can increase the chill, despite the 50-inch snowfall being low for the state. Homeowners should plan for warmer summers compared to the rest of Vermont.
Frequently Asked Questions
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Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020.
Climate normals are 30-year averages of weather variables computed from 1991 to 2020. Station data is aggregated to county level using spatial averaging. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.