Frost alerts

A heads-up before the frost, not after it

Pick your town and we’ll email you on the afternoons when a frost is likely there that night, and when Met Éireann issues a warning for your county that matters in the garden. Free, and nothing on the nights you don’t need it.

Frost on red leaves in the early morning

What you’ll get

  • Frost likely tonight. When the forecast for your town points to a ground frost after a run of ten or more frost-free nights. That’s usually the first frost of autumn, or a frost that comes back after a mild spell in spring, the ones that catch out plants you’ve already put out.
  • Frosts in May and September. These are the months when tender plants are most likely to be outside, so we’ll tell you about any frost then, not just the first.
  • Met Éireann warnings for your county. Low temperature, snow and ice warnings, and orange or red wind warnings. Each comes with the warning text as Met Éireann issued it, and a few garden jobs worth doing before it arrives.

Frost emails go out at around 3pm, which leaves time to get the fleece out before dark. We send them from September to May.

How often?

Not very. Ground frost is common in Ireland: Met Éireann’s inland weather stations record a grass frost on about 70 to 105 nights a year. An email for every one of those would be no use to anyone, so we only send the frosts that are worth acting on. Going by the last ten years of records from 17 Met Éireann weather stations, that works out at roughly two to seven frost emails a year, depending on where you are, plus any warnings.

How it works, and what it can’t do

Each afternoon we take Met Éireann’s forecast for your town: the lowest air temperature overnight, the cloud cover and the wind. Frost forms at ground level first, and on a clear, still night the grass can be several degrees colder than the air. So we estimate the grass temperature from those three numbers, using a formula we worked out from ten years of Met Éireann station records of air and grass temperatures.

It’s an estimate, and it’s for your town, not your garden. Low ground, hollows and open beds get frost before anywhere else, and a sheltered bed against the house may escape it. Treat an alert as a reason to check your garden, not a promise.

Forecasts and warnings: Copyright Met Éireann. Source met.ie. Published under the Met Éireann Custom Open Data Licence. Met Éireann does not accept any liability whatsoever for any error or omission in the data, their availability, or for any loss or damage arising from their use. Modified: the ground frost estimate is our own calculation from Met Éireann’s forecast air temperature, cloud cover and wind. Warnings are reproduced unchanged. Town names and locations from GeoNames (CC BY 4.0).