The most important factor in determining when to plant a certain type of vegetable in your garden is the “Last Freeze Date” in the spring, and the “First Freeze Date” in the fall for your area. These dates for a given area are based on historical weather data from that area over a 30 year period compiled by the National Climatic Data Center.
The actual dates that the freezing temperatures occurred each year in a given area, during this 30 year period, are averaged together. Probabilities of a freeze occurring are then assigned to these average dates.
The first column shows the City and State name.
The second column shows three temperatures. The first temperature, 36°F, is the Frost temperature. Temperature monitoring stations are typically mounted four to six feet above the ground. During clear, calm, and cold nights the temperature at ground level, where your garden is, can become much colder. The second temperature, 32°F, is the Freeze temperature. The third temperature is the Hard Freeze temperature.
The third column titled Spring Date has three sub-columns in it titled Probability Level 90, 50, and 10 with dates listed under them. The lower the probability level number, the less likely it is that a Frost, Freeze, or Hard Freeze will occur on that date.
The Last Freeze Date for this example is April 10. This means that there is only a 10 percent chance that it will freeze on this date. Remember, although statistically accurate, you are really just playing the odds with this date. Before planting you should ALWAYS check your local weather to see if a freeze is in the forecast.
In the table below, click on your state specific data then look for your city’s information in the next screen.
I hope you find this information helpful and I wish you Happy (freeze damage free) Planting.
Data Source: National Climatic Data Center