Select your state from the list and search for your town/city in the data sheet. If yours isn’t listed, look for the town/city nearest you that shares a similar climate and altitude.
The Freeze/Frost Occurrence Data can be a little confusing the first time you view it, so this is the method I use to extract my average frost dates:
1. Under the Threshold column, use the 32°F row data. 2. Under the Spring (Date), Fall (Date), and Freeze Free Period (Days) columns, use the 50% Probability Level data.
Cross-reference the values to get your frost dates and the length of your growing season. The date in spring is known as your last freeze. The date in fall is your first freeze. The days in between equal the length of your frost-free growing season.
For example, in the illustration above, the town of Adel has a 50% probability of a freeze happening on June 6 and September 17. That means the average last frost is June 6 and the average first frost is September 17, giving me an approximate 102-day growing season.