Frost Date Calculator: Last & First Frost by Location
Pick your nearest city to see the typical date of the last spring frost, the first fall frost, and how many frost-free days usually fall in between — plus, if you enter a date, the estimated chance frost still lands on it.
Based on typical 30-year climate averages, not this year's forecast. Local microclimates, elevation and shelter can shift your actual frost dates by a week or more — your county extension office or national weather service usually has more precise records.
How average frost dates are worked out
Weather services track the last spring day and first fall day each year that the temperature drops to 32°F (0°C) or below at a given station, then average that date over roughly 30 years of records. That average is a useful planning guide, but any single year can land well before or after it — some years bring a late spring frost that kills tender seedlings, others stay mild for weeks longer than usual.
To capture that spread, this calculator also uses the station's typical year-to-year variation (its standard deviation) to work out a 10%-risk and a 90%-risk date on each side of the average, the same approach agricultural extension services use when publishing planting guides.
Reading the three dates
For the last spring frost: the earliest date is roughly how soon a mild year might clear frost, but there's still a good chance of frost after it. The average date is the 50/50 midpoint. The latest date is a cautious choice — only about a 10% chance of frost after it — which is why many gardening guides tell you to wait until "two weeks after your average last frost" for the most tender plants.
For the first fall frost, the logic mirrors it: the earliest date is when frost risk starts to appear, the average is the 50/50 point, and the latest date is when frost has almost certainly already arrived. The days between the last spring frost and the first fall frost make up your growing season.
Limits of a frost date calculator
These are historical averages for a nearby weather station, not a forecast for this specific year. Local microclimates matter a lot: low-lying areas collect cold air and frost earlier, being near a large body of water or a city delays frost, and elevation changes shift dates by days for every few hundred feet. A frost is also not one fixed event — a light frost (32°F) can nip tender seedlings while many vegetables tolerate it, whereas a hard freeze (28°F or below) damages far more.
For your exact local numbers, your country's meteorological service or a local agricultural extension office usually publishes station-level data more precise than a citywide average.
Frequently asked questions
- What is a frost date?
- It's the average date, based on around 30 years of records, when a location's temperature last drops to 32°F (0°C) in spring or first drops to it in fall. It's a planning guide, not a guaranteed date.
- When is it safe to plant after the last frost?
- Many tender vegetables (tomatoes, peppers, beans) are usually planted a week or two after the average last frost date, or from this calculator's later, lower-risk date if you want more of a safety margin.
- What do the 10%, 50% and 90% dates mean?
- They're probability estimates from the location's historical spread. The 50% date is the plain average. The safer date has only about a 10% chance of frost occurring after it (for spring) or before it (for fall); the riskier date has about a 90% chance.
- What's the difference between a frost and a freeze?
- A light frost forms around 32°F (0°C) and can damage tender plants while many hardy ones survive. A hard freeze, 28°F (−2°C) or below, kills most garden plants outright. Frost dates here track the lighter 32°F threshold.
- Why does my actual frost date differ from the calculator?
- Frost is very local. Low-lying yards, open fields and rural areas frost earlier and harder than nearby hills, coastlines or city centres, which can shift the real date by a week or more from a citywide average.