Jefferson County Climate
Jefferson County, New York
Avg Annual Temp
45.8°F
Annual Precip
40.7"
Annual Snowfall
116.4"
Extreme Heat Days
2.95
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Jefferson County Weather
Lake Ontario's Heavy Influence
Jefferson's 45.8°F average temperature is slightly below the national median, but its 116.4 inches of snow is exceptional. This lake-effect climate creates dramatic winter weather shifts.
Cooler and Much Snowier
The county is slightly cooler than the New York average of 47.4°F but is among the state leaders for snowfall. Its 116.4 inches of annual snow is nearly triple the state's typical accumulation.
Warmer than the Adirondacks
Jefferson is warmer than neighboring Franklin (41.3°F) and Hamilton (41.0°F) due to lake moderation. However, it faces more snow than Franklin, though less than the extreme totals in Herkimer.
A Classic Lake-Effect Cycle
July is warm at 70.0°F with only 3 days of extreme heat. January dips to 19.9°F, bringing the bulk of the county's 116.4 inches of annual snowfall.
Winterize Against the Wind
Focus on high-quality weatherstripping and insulation to combat the lake-effect winds. Maintain reliable snow removal services to manage the frequent and heavy 116-inch annual snowfall.
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.