USDA Hardiness Zone –First Frost Date- Last Frost Date
Zone 1 -July 15th -June 15th
Zone 2 -August 15th- May 15th
Zone 3 -September 15th May 15th
Zone 4 -September 15th May 15th
Zone 5 -October 15th April 15th
Zone 6 -October 15th April 15th
Zone 7 -October 15th April 15th
Zone 8 -November 15th March 15th
Zone 9 -December 15th February 15th
Zone 10 -December 15th January 31st (sometimes earlier)
Zone 11 -No frost. No frost.
You can look up your climate zone here: http://planthardiness.ars.usda.gov/PHZMWeb/