Grinnell, IA Climate

Climate Insight: Grinnell, IA

The NOAA 1991–2020 climate normals describe Grinnell, Iowa as a location with an annual average temperature of 48°F, ranging from a mean daily high of 58°F to a mean daily low of 37°F. July is typically the warmest month of the year, while January is the coldest. These thirty-year averages, computed from station USC00133473, smooth out year-to-year variability and give a baseline expectation for typical conditions in any given month.

Precipitation patterns matter as much as temperature for anyone planning to live, garden, or travel here. Grinnell receives roughly 38.2 inches of precipitation each year, with 31.0 inches typically falling as snow. Growing-season length varies with elevation and microclimate, with the last spring freeze near May 3 and the first fall freeze near October 6. For energy use, 7,038 heating degree days and 692 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.

On PlainClimate's composite comfort index, Grinnell scores 62/100 (Good), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. Use the monthly tables above to plan around specific windows — shoulder seasons for mild highs and lows, peak summer for July-driven heat, or deep winter for January-driven cold. All figures here are thirty-year averages: any single year may run warmer, wetter, drier, or cooler than the normal, so treat them as planning guidance rather than forecasts.