A single named point, not a zip code or a whole region.
Dates are medians and percentiles from daily minima, 1991 to 2020.
Event
Early (1 year in 10)
Median
Late (9 years in 10)
First autumn frost
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Last spring frost
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When is the first frost where I live?
Pick the nearest point above and you get the median first autumn frost from 1991 to 2020, with the early and late ends of the range. The median is a coin flip — half of all years frost before it — so the window matters more than the date itself.
How to read the result
The number in large type is the median — the date by which half of the last 30 years had seen their first autumn frost. It is a coin flip, not a deadline.
The table gives the shape of the distribution:
Early is the 10th percentile. Frost this soon in about one year in ten.
Median is the 50th percentile, the headline date.
Late is the 90th percentile. By this date, frost has almost certainly happened.
If you plan against the median you will be caught out in half of all years. Plan against the early date and treat the median as the point where it becomes likely rather than possible.
Air frost, not ground frost
These dates are air frost: the daily minimum air temperature reaching 0 °C at the standard measuring height of about 1.5 metres, shaded and ventilated.
Ground frost arrives earlier and more often. On a clear, still night the ground and low foliage radiate heat directly to the sky and end up two to four degrees below the air above them. So your lawn, your car roof and your tender bedding will whiten on nights when the official minimum never reached freezing.
For a gardener that is the more important number, and it means the practical trigger sits above zero — treat a forecast low of 3 °C or below on a clear calm night as a possible frost. The mechanism is in at what temperature frost forms.
Why there is no zip code box
The search term people use is "first frost date by zip code", and this lookup deliberately does not offer one.
A zip code covers an area, sometimes a large and topographically varied one, and turning it into a single point requires a centroid dataset this site does not carry. A result derived that way would look more precise than it is while quietly picking a point for you.
Naming the point instead is more honest and no less useful, because either way the real work is adjusting for your own garden — which the published date cannot do for you.
Adjusting for your own site
The difference between one end of a garden and the other can exceed the difference between towns.
Frost earlier than the nearest point: valley bottoms and hollows, the low corner of a slope, open ground with a clear view of the sky, behind a solid fence across a slope, and anywhere noticeably higher in elevation.
Frost later: against a south or west-facing wall, under a tree canopy or pergola, close to a building, beside a large body of water, and inside a town rather than outside it.
Write down the date of your first frost and the forecast low that night. After two or three years you will know both your own date and your own offset from the forecast, which is the one piece of information no published dataset has.
What the dates mean for the calendar
Working backwards from your own early date:
Six weeks before: start planning what comes in and what gets covered, and check you have fleece.
Three weeks before: bring in anything with a chilling threshold above 10 °C — peppers, citrus, houseplants that summered outside. They are damaged well before any frost, which is covered in overwintering plants.
From the early date: watch the overnight lows every clear evening.
On the night: water the soil in the afternoon, cover before dusk, move containers against a wall — when to cover your plants.
After the first hard freeze: lift tender bulbs and accept the season for the annuals.
Common questions
Why is there no zip code search?+
Because there is no zip-to-coordinate dataset in this site, and pretending otherwise would mean guessing which point a zip code maps to. The lookup offers named points with real 30-year records behind them instead. Pick the nearest one and adjust for your own site, which you would have to do with a zip result anyway.
What does the early and late range mean?+
The early column is the 10th percentile — frost this soon in about one year in ten. The late column is the 90th percentile. The median in the middle is the date by which half of all years had frosted. Planning against the median means being caught out half the time, so the early date is the more useful planning figure.
Is this air frost or ground frost?+
Air frost: the date the daily minimum air temperature reached 0 °C at standard measuring height. Ground frost happens earlier and more often, because on a clear still night the surface radiates heat and ends up two to four degrees colder than the air above it. Your lawn will whiten before these dates.
Where does the data come from?+
Daily minimum temperatures for 1991 to 2020 from the ERA5 reanalysis, retrieved through the Open-Meteo archive. That is the same 30-year window standard climate normals use. For each year the first autumn and last spring dates below freezing are found, and the percentiles are taken across the 30 years.
Why is my garden different from the nearest point?+
Because elevation, shelter, surfaces and cold-air drainage all move the local figure, often by more than the difference between neighbouring towns. A valley bottom frosts weeks earlier than a slope above it; a bed against a south-facing wall frosts weeks later. Keeping your own record for two seasons beats any published figure.
