Last Frost 2014: 9 May
First Frost 2014: 29 Sep
Growing Season: 173 days

Last Frost - 10: 29 Apr
Last Frost - 20: 19 Apr
Last Frost - 30: 09 Apr
Last Frost - 40: 30 Mar
Last Frost - 50: 20 Mar
Last Frost - 60: 10 Mar
Last Frost - 70: 28 Feb
Last Frost - 80: 18 Feb
Last Frost - 90: 08 Feb
Last Frost - 100: 29 Jan

Zip code 20171, Herndon VA is in USDA Hardiness Zone 6b: -5F to 0F. Using updated climate data through 2010, 20171 is in the Plantmaps Hardiness Zone 6b: -5F to 0F. The average first frost in 20171 is between October 11 - 20, while the average last frost occurs between April 21 - 31. 20171 is part of Ecoregion 64a - Triassic Lowlands. 20171 averages 31 - 45 days per year where the temperatue exceeds 86°F. The average annual high temperature in 20171 is 66°F and the average annual low temperature is 43°F. The average high temperature in July (Summer) is 86°F, while the average high temperature in January (Winter) is 42°F. Reference

I also came across this interesting statistics page while researching: http://www.zipdatamaps.com/20171

Tags: Garden, Statistics