Before you start planting, consider the frost date for your growing zone. (Click here to access the USDA Hardiness Zone Map to determine your city or region’s growing zone.) Frost dates are based on historical data compiled by the United States Department of Agriculture.
The probability of frost or freeze is greatly affected by elevation, the direction of sunlight (north, south, east or west), winds, and other factors. The National Climatic Data Center offers a number of frost/freeze maps. Be sure to check them out â€“ theyâ€™ll tell you the rough date of the first and last frost for your area, so you know when you can start planting outdoors and when to finish harvesting for the year. Be aware that the chance of an early or late frost without warning is always a possibility.
Frost usually occurs on clear nights, when heat comes up from the ground. Small ice crystals form when water vapor condenses. Like with dew, the temperature at ground level is crucial â€“ the temperature there is often colder than the air temperature just a few feet higher. Tender plants that cannot withstand extreme cold must be covered to be protected from frost.
Following are the average last frost dates by zone:
Zone 1 – Frost potential 365 days a year
Zone 2- Last frost date May 1 – May 31
Zone 3 – May 1 – May 31
Zone 4 – May 1 – May 31
Zone 5 – March 31 – April 30
Zone 6 – March 31 – April 30
Zone 7 – March 31 – April 30
Zone 8 – February 28 – March 31
Zone 9 – January 31 – February 28
Zone 10 – January 31 or sooner
Zone 11 – No Frost
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