Frost dates in Hiroshima: last spring frost and first autumn frost
When is it safe to plant out in Hiroshima, and when does the first frost come? Dates from 45 years of nightly minimum temperatures (1981–2025), with how early or late they can fall.
Frost dates in Hiroshima and how sure they are
| Early year (1 in 10) | Typical (median) | Late year (1 in 10) | |
|---|---|---|---|
| Last spring frost | 7 March | 22 March | 5 April |
| First autumn frost | 28 November | 14 December | 25 December |
In a typical year the last frost in Hiroshima falls around 22 March and the first one around 14 December, leaving about 265 frost-free days (between 244 and 286 in 8 years out of 10). To be safe, plant tender crops after 5 April: by then the last frost has passed in 9 years out of 10. Bring them in before 28 November: in 1 year in 10 the first frost comes earlier.
Frost month by month in Hiroshima
| Month | Average low | Coldest night (avg) | Record low | Frost nights | Years with frost |
|---|---|---|---|---|---|
| January | 0.5 °C | -2.9 °C | -5.3 °C | 14 | 98% |
| February | 0.7 °C | -2.7 °C | -7.5 °C | 12.8 | 100% |
| March | 3.2 °C | -1.5 °C | -4.1 °C | 5.8 | 98% |
| April | 8 °C | 1 °C | -1.5 °C | 0.3 | 18% |
| May | 13 °C | 7.3 °C | 4 °C | 0 | 0% |
| June | 18.1 °C | 12.9 °C | 9.6 °C | 0 | 0% |
| July | 22.8 °C | 18.7 °C | 12.9 °C | 0 | 0% |
| August | 23.6 °C | 19.6 °C | 15.3 °C | 0 | 0% |
| September | 19.5 °C | 13.6 °C | 7.6 °C | 0 | 0% |
| October | 12.8 °C | 6.7 °C | 3.9 °C | 0 | 0% |
| November | 7.3 °C | 1.7 °C | -1 °C | 0.2 | 13% |
| December | 2.4 °C | -1.3 °C | -4 °C | 5.6 | 98% |
Frost here means a night minimum at or below 0 °C at 2 m. Frost nights is the average count per month; years with frost is how many years had at least one.
Frost alerts for your garden or field
LayEarth Business Agro sends an alert when the forecast low at your saved site drops below your threshold (0 °C by default), with frost risk, hours below zero and white or black frost for each forecast day. LayEarth Pro, from 9 USD a month, adds alerts for the places you follow.
Temperature map around Hiroshima
The live temperature layer of the map (NOAA GFS forecast): watch the cold nights coming hour by hour.
More for Hiroshima
Will it rain today in Hiroshima? · Open the temperature map on Hiroshima
Questions
- When is the last frost in Hiroshima?
- On average around 22 March. In an early year the last frost comes by 7 March, in a late one (1 year in 10) after 5 April.
- When is the first frost in Hiroshima?
- On average around 14 December. In 1 year in 10 it comes before 28 November, in a mild year not until 25 December.
- How long is the growing season in Hiroshima?
- About 265 frost-free days between the last spring frost and the first autumn frost, from 244 in a short year to 286 in a long one.
- When can I plant tomatoes in Hiroshima?
- Frost-tender plants such as tomatoes, peppers, beans and courgettes go out after the last frost: after 5 April the risk is down to 1 year in 10. Hardy crops can go earlier.
- How cold does it get in Hiroshima?
- The coldest night of winter averages -3.4 °C; the lowest since 1981 was -5.6 °C in 1984.
Frost dates nearby
How these dates are computed
Daily minimum temperature at 2 m from NASA POWER (MERRA-2 reanalysis, public domain), 1981–2025, corrected from the ~50 km grid to the real altitude of Hiroshima (6.5 °C per km). For each year: the last night at or below 0 °C before midsummer and the first one after it; the dates are the median and the 10% / 90% of those years. A garden in a frost pocket or a city centre can differ by days. Live temperatures: the temperature layer of the map.