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The map above shows the average date of the last frost in spring. Use it to help plan when you will transplant plants that are not frost-tolerant.
Keep in mind that the dates are guides, and no guarantee that frost will not occur after the last date shown. In fact, chances are that in half the years, you will experience frost after the average last frost date.
This map does not tell you the best time to plant tomatoes or other frost sensitive crops. That date is usually several weeks after the last frost, after the soil has warmed and nighttime temperatures are reliably well above freezing.
Also remember that microclimates have a tremendous effect on frost. Some valleys and low-lying areas can be plagued by late frosts well after the last spring frost date on cold nights when there is radiational cooling. Large bodies of water may moderate air temperatures at some sites, reducing the chances of frost.
Contact your county's Cornell Cooperative Extension staff for local advice on frost and microclimates. Some counties provide more specific weather information or detailed maps for their area, including:
Please send others to: Craig Cramer firstname.lastname@example.org.
National frost and frost-free season maps are available from the NOAA National Climatic Data Center.
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