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Basil Growing Season for Illinois

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
ILAdams5/07145
ILAlexander4/21177
ILBureau5/19127
ILCarroll6/0894
ILChampaign5/12142
ILChristian5/12141
ILClay5/17137
ILClinton5/03156
ILColes5/18136
ILCook5/26125
ILCrawford5/22130
ILDekalb5/27118
ILDouglas5/16137
ILDupage5/31116
ILEdgar5/16139
ILEdwards5/02160
ILEffingham5/14138
ILFord5/21125
ILFranklin5/09150
ILFulton5/16133
ILGreene5/10141
ILHamilton5/09145
ILHancock5/14133
ILHardin5/10140
ILHenderson5/15141
ILHenry5/16136
ILIroquois5/28120
ILJackson5/10142
ILJasper5/13141
ILJefferson5/13141
ILJersey5/15135
ILJo Daviess5/24117
ILKane5/30122
ILKnox5/18134
ILLa Salle5/20135
ILLake6/04114
ILLee5/27121
ILLivingston5/15141
ILLogan5/16136
ILMacon5/20130
ILMacoupin5/16137
ILMadison4/25168
ILMarion5/11144
ILMarshall5/30120
ILMason5/14140
ILMassac5/04156
ILMchenry6/01111
ILMclean5/23128
ILMercer5/20131
ILMonroe5/06151
ILMontgomery5/09145
ILMorgan5/21129
ILPeoria5/21134
ILPerry5/10146
ILPope5/10146
ILPutnam5/29116
ILRandolph5/09146
ILRichland5/16138
ILRock Island5/23128
ILSaline5/09150
ILSangamon5/10142
ILSchuyler5/19132
ILShelby5/12141
ILSt. Clair5/12136
ILUnion5/03157
ILVermilion5/23132
ILWabash5/09142
ILWarren5/20131
ILWashington5/04150
ILWayne5/16137
ILWhiteside5/25121
ILWinnebago5/26121
ILWoodford5/23127