COLUMBIA, Mo. – The free online Missouri Frost/Freeze Probabilities Guide helps farmers and gardeners make planting decisions.

University of Missouri Extension integrated pest management specialists created the website at ipm.missouri.edu/FrostFreezeGuide. The guide is also available as a free downloadable PDF.

Both provide frost and freeze probabilities, tables, maps and dates for the 103 National Weather Service cooperative weather stations in Missouri, said MU Extension climatologist Pat Guinan.

The National Centers for Environmental Information provides information based on data for 1981-2010.

The Missouri growing season typically runs from April to October. Where you live in Missouri makes a big difference in when the first or last freeze occurs, said Guinan.

Climatologists can predict frost timing based on temperature records and the region’s topography.

The median date maps provide the last spring and first fall median frost/freeze dates for specific temperature thresholds. In this guide, climatologists define the median date as the date when there is a 50 percent chance a frost or freeze temperature will occur before or after a given date.

Extreme date maps give the latest spring and earliest fall frost and freeze dates using weather stations with more than 100 years of temperature observations.

The weather station map and probabilities table show data and probability thresholds for weather stations across the state. You can search for the location nearest you by using the weather station search tool, Guinan said.