Planting Dates & Frost Calculator (South Africa)

Typically around 5 September, though it varies year to year. To be safe rather than typical, this tool suggests waiting until around 22 September before planting out anything frost-tender, which is that extra margin built in on purpose rather than a single best-guess date.

Pretoria's typical last frost is around 5 September, and the safe date this tool suggests planting out on is 22 September. Frost returns around 6 June, which leaves about 275 frost-free days in between. Gauteng's other listed towns sit within a few days of that, since they share an altitude and a distance from the coast.

That question usually means a USDA hardiness zone, and it is the wrong tool for this job in South Africa. A hardiness zone is built from the average annual coldest night, so it tells you whether a perennial will survive the winter. It says nothing about when frost stops in spring, which is the date a vegetable gardener actually needs. It also flattens South Africa badly, since altitude does more to our frost risk than latitude does, and the widely quoted zone numbers for South African cities come from overseas maps that were never fitted to local data. A last-frost date is the answer to the question people are really asking.

Light frost is a screen minimum temperature at or below 2 degrees Celsius, enough to damage tender seedlings like tomatoes and beans. Moderate frost, the standard definition and this tool's default, is at or below 0 degrees. Hard frost is at or below minus 2 degrees, cold enough to damage even hardy, established plants.

Because the calibrated typical date still runs a measured bias in the unsafe direction: at the weather stations this tool was checked against, the typical last-frost date came out too early and the typical first-frost date too late. The safe dates already have enough margin built in, 16 days later for last frost and 9 days earlier for first frost, to cover most of those stations rather than only the average one, so you can plant to whichever date suits how much risk you want to take.

It depends on the town, and this tool says which for each one. Two towns, Bethlehem and Bloemfontein, are cross-checked against a nearby weather station. Every other listed town is calibrated against South Africa's national frost surface instead, which typically comes within about 7 days of a real station where both exist, with a worst case of about 21 days. That gap is exactly why the safe date carries its own margin.

Only towns with a real frost reference to calibrate against are listed, 36 of them. An uncalibrated frost date would not be a safer guess, it would just be an unchecked one, and this tool would rather leave a town out than print a date nobody verified. If your town is missing, pick the listed one closest to you in altitude and distance from the coast, which affects frost far more than it affects rainfall.

No. South Africa's national frost surface has no dated frost band for Cape Town's true city-bowl coordinate, so rather than guess or borrow a nearby town's number, this tool leaves it out entirely.

The number of days between the last frost of spring and the first frost of the following autumn, the stretch when frost-tender crops can generally stay in the ground. In Johannesburg on the standard threshold that is about 274 days.

12 of the 36 listed towns, all in the warmer coastal and lowveld parts of the country, including Durban, Richards Bay and Gqeberha. South Africa's national frost surface flags these as rarely or never getting regular frost rather than giving them a first or last date, so this tool follows that rather than forcing a date onto a town that does not reliably have one. An unusually cold, still, clear night can still bring a light touch of frost in most of them, just not on a predictable date.

No. It is what the long-term record says is typical for your town, which is the right baseline for deciding roughly when to plant, not for a specific week. Always check a real short-range forecast before you actually plant out or bring plants in.

Daily minimum temperature from the Open-Meteo ERA5 archive, corrected against South Africa's ARC-ISCW national frost surface and, for two towns, cross-checked against published weather-station frost dates from Moeletsi, Tongwane and Tsubo's 2016 study of frost in the Free State. Raw satellite-reanalysis data alone runs frost dates five to eight weeks off in the unsafe direction if used uncorrected, so every date on this page is calibrated against a real reference, never used raw.

Because a colder threshold is reached on fewer nights. Light frost is the widest window: it starts earliest in autumn and ends latest in spring. Hard frost is the narrowest, since a night has to get considerably colder for it to count.

No. It tells you what is typical for your town across many years, which is the right tool for planning months ahead, booking seedling trays, or deciding when a nursery should stop stocking tender plants. In the week before you actually plant, check a real short-range forecast instead.