About Last Frost Day

A free tool for one question every gardener asks: when is it safe to plant?

Most frost-date sites give a single "average last frost" date. That date is a coin flip: in about half of years, frost comes later. Last Frost Day shows the full range of probabilities from NOAA's official climate data so you can decide how much risk you want to take with your tomatoes.

How the site is built

• Data, not opinions. Frost dates come from NOAA NCEI's 1991–2020 U.S. Climate Normals. Hardiness zones come from the 2023 USDA Plant Hardiness Zone ZIP listing by the PRISM Climate Group at Oregon State University. See the methodology.
• Built and maintained with AI assistance. The code, the data processing and the written content are produced with the help of AI tools.
• Human-reviewed. A person reviews the site and its content before publishing.
• No invented experts. There's no made-up gardener persona here. Where we give growing advice in the future, we will cite university extension services.

Last Frost Day is independent and not affiliated with NOAA, USDA or Oregon State University.