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Basil Growing Season for Washington

The NOAA National Climatic Data Center provides information to the public about spring and fall frost dates in the United States and the length of the expected growing season for each area. These statistics are calculated using data collected from 1971 to 2000, across 4300 weather stations located in every part of the country.

While informative, the statistics that NOAA provides is overwhelming. So, we took the liberty of extracting the most basic information that we feel would be useful to someone interested in growing basil outdoors.

The table below lists the date after which it should be safe to plant basil outdoors in each area of the state. This information is based on NOAA’s calculations for a 10% probability of temperatures falling below 36 degrees Fahrenheit. This means that, on average, there is only a 10% chance that you will see frost after this date. Also listed is the estimated length of the growing season. This is how many days you can expect to have before the risk of frost is greater than 10%.

Please use this information at your own risk. You must take into consideration many varying factors, for example, micro-climates or the presence of valleys and bodies of water, to determine your actual growing season.

StateCountyLast Frost DateLength of Growing Season
WAAdams6/2182
WABenton5/11153
WAChelan5/15139
WAClallam6/06103
WAClark6/06105
WAColumbia6/04111
WACowlitz5/27137
WADouglas5/15139
WAFerry7/1044
WAFranklin6/01110
WAGarfield6/1392
WAGrant5/28122
WAGrays Harbor6/09107
WAIsland5/22133
WAJefferson6/1989
WAKing6/07114
WAKitsap5/11158
WAKittitas6/1785
WAKlickitat5/16137
WALewis6/2877
WALincoln7/0850
WAOkanogan6/2185
WAPacific6/2580
WAPend Oreille7/2036
WAPierce8/032
WASan Juan5/10164
WASkagit5/19123
WASkamania7/1242
WASnohomish6/02115
WASpokane6/09103
WAStevens6/2872
WAThurston6/1589
WAWalla Walla6/2376
WAWhatcom5/18147
WAWhitman7/0460
WAYakima5/27122