Johnston Iowa Climate Data

Monthly Average Climate Data for Johnston Iowa

Switch Data to Celsius/Metric Units
MonthAvg. LowAvg. HighAvg. Precip
January12.7 °F30.2 °F1.01 in.
February16.5 °F34.8 °F1.22 in.
March27.7 °F47.8 °F2.15 in.
April39.1 °F61.8 °F3.84 in.
May51.0 °F72.1 °F5.0 in.
June61.3 °F81.7 °F5.31 in.
July65.2 °F85.7 °F4.24 in.
August62.6 °F83.8 °F4.21 in.
September53.9 °F77.5 °F3.4 in.
October41.5 °F64.1 °F2.67 in.
November29.3 °F48.8 °F1.85 in.
December18.5 °F35.5 °F1.43 in.
Annual39.9 °F60.3 °F36.33 in.

Climate Data for Johnston Iowa

Average First Frost DateOct. 11 - Oct. 20
Average Last Frost DateMay 1 - May 10
Average Days With Frost125-150 Days
Plant Hardiness Zone - 2023Zone 5b : -15°F to -10°F
Plant Hardiness Zone - 2012Zone 5a : -20°F to -15°F
Current Drought ConditionsAbnormally Dry
Köppen Climate ClassificationDfa - Humid Continental Hot Summers With Year Around Precipitation