About Frost Calendar

Frost Calendar is a small independent project at frostcalendar.com. For each U.S. city it covers, it shows the typical last spring and first fall frost dates, the length of the growing season and the USDA hardiness zone, with a vegetable planting calendar where frost dates apply.

Where the data comes from

• Frost and freeze odds, growing season and growing degree days: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020.
• Hardiness zones: USDA Plant Hardiness Zone ZIP tables (2023 and 2012) published by the PRISM Group, Oregon State University. This site does not show the official USDA map.
• City boundaries, ZIP areas and populations: U.S. Census Bureau. Elevations: U.S. Geological Survey.
• Planting rules: published Cooperative Extension guidance, quoted with a link to each source.

How pages are made

Every page is generated automatically by a script from these public data (NOAA climate normals, PRISM zone tables). The script reads or calculates every number. The sentences that explain the numbers are written ahead of time as a fixed set of rules, and each one appears only when a city's data meets its condition. Nothing is written on the fly. No one reviews each page on an ongoing basis. Samples of the generated pages are spot-checked against other published frost-date sources. The methodology lists the rules and their sources.

Frost dates are long-term odds, not forecasts. Check your local forecast before you plant.

For questions or corrections, see Contact.