Johnson County Climate
Johnson County, Iowa
NOAA NCEI 1991-2020 Climate NormalsAvg Annual Temp
50.0°F
Annual Precip
37.1"
Annual Snowfall
28.4"
Extreme Heat Days
22
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Growing Season & Gardening
5b
Minimum winter temperature range for plant survival
3,245
Supports most vegetables & fruits
Seasonal Overview
National Comparison
7-Day Outlook
Forecast
Current Conditions
Air Quality
Safety
Weather Alerts
Climate Advisory: Johnson County
Climate Verdict
Johnson County has a cool, averaging 50.0°F annually, moderate rainfall of 37.1 inches per year, occasional hot days — 21.6 per year above 90°F, moderate snowfall of 28.4 inches annually. This climate profile shapes everything from energy costs to outdoor recreation opportunities.
Seasonal Breakdown
Winters are very cold — January averages 21.6°F. summers are warm — July averages 74.7°F. Residents experience a substantial 53°F difference between winter and summer.
Outdoor & Gardening Guidance
Growing season and gardening data is currently limited for Johnson County. Check the USDA Plant Hardiness Zone Map and local extension office for specific guidance.
Regional Context
Johnson County closely matches the Iowa statewide average temperature of 48.0°F.
Climate Profile
About Johnson County Weather
Johnson County's Variable Climate
Johnson County averages 50.0°F annually, falling just below the national median. This region is characterized by significant seasonal shifts and robust annual precipitation of 37.1 inches.
A Warm Spot in Iowa
Johnson is notably warmer than the state average, exceeding the 48.0°F Iowa norm by two degrees. It is also wetter than average, receiving 37.1 inches of rain and snow combined.
Warmer than Northern Neighbors
The county is three degrees warmer on average than Jones County to its north. It experiences 22 days of extreme heat, making it a warmer corridor in the eastern part of the state.
Hot Summers and Snowy Winters
July temperatures average 74.7°F, contributing to 22 extreme heat days over 90°F. Winters are cold, bringing 28.4 inches of snowfall and an average low of 21.6°F in January.
Equip for Heat and Ice
With over three weeks of 90°F weather, reliable cooling is essential for summer safety. Residents should also keep ice melt and snow shovels ready for the 28.4 inches of annual snow.
Frequently Asked Questions
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Data sources: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020. Forecast and alert data from National Weather Service API. Air quality data from Open-Meteo.
Climate normals are 30-year averages of weather variables. Station data is aggregated to county level. Forecasts and alerts are fetched live and may change frequently. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.