Figure 1. Low risk (10%) of a 32°F spring freeze occurring after the range of dates listed, based on 30 years of data. (Source: High Plains Regional Climate Center) (All maps link to larger versions.)
Figure 2. Medium risk (50%) of a 32°F spring freeze occurring after the range of dates listed, based on 30 years of data. (Source: High Plains Regional Climate Center)

Figure 3. High risk (90%) of a 32°F spring freeze occurring after the range of dates listed, based on 30 years of data. . (Source: High Plains Regional Climate Center)
As spring planting approaches, it is important to understand factors that influence planting decisions. In addition to environmental and agronomic factors such as the crop planted, calendar date, soil temperature, and soil moisture, a major climatic factor is spring freeze risk. While each season is different from the previous ones, long-term average (30 years) spring freeze risks calculated based on available historic data provide valuable information for making planting decisions.
Figures 1 to 3 were generated from High Plains Regional Climate Center data which shows an average date when spring freeze risk (32ºF) is low (10%), medium (50%), and high (90%), respectively. Please note that this information is not a recommendation as to when to plant, but rather provides general probabilities for spring freeze, which in turn can be used when making planting decisions. Regardless of calendar date or frost probability on any specific date, examine the short-term weather forecast for the probably of a cold spell and/or spring frosts occurring prior to or after crop emergence. If a cold spell is forecast, you may choose to delay planting even if the calendar date is normally conducive for planting.
Tapan Pathak
Extension Educator for Climate Variability