WEATHER · CLIMATE NORMALS · 1991–2020
Johannesburg Climate — Averages by Month
What the weather in Johannesburg, ZAaverages across a standard 30-year period. Each month's figure is the 1991–2020 mean temperature and total rainfall from the ERA5 reanalysis — the long-run normal a place settles around, not a forecast for any particular day.
Month-by-month normals
| Month | Avg temperature | Avg rainfall |
|---|---|---|
| January | 20.2 °C · warmest | 137.8 mm |
| February | 19.9 °C | 116.0 mm |
| March | 18.5 °C | 94.0 mm |
| April | 15.6 °C | 48.5 mm |
| May | 12.5 °C | 18.0 mm |
| June | 9.7 °C | 8.4 mm |
| July | 9.5 °C · coldest | 3.7 mm |
| August | 12.7 °C | 10.7 mm |
| September | 16.8 °C | 24.2 mm |
| October | 18.5 °C | 79.5 mm |
| November | 19.1 °C | 105.4 mm |
| December | 19.9 °C | 144.6 mm · wettest |
How to read these numbers
These are reanalysis normals, not readings from a single weather station. They come from the ERA5 0.25° (~25 km) global reanalysis grid, sampled at the grid cell nearest Johannesburg — centred at 26.25°S, 28.00°E. A reanalysis blends observations with a physics model onto an even grid, so a coastal or mountain city's cell can read a little cooler, warmer, wetter or drier than the city centre itself. The month-to-month shape — when it's hot, when it rains — is what these normals capture best.
“Normal” means the 1991–2020 average, the current World Meteorological Organization standard period. A normal is what a place tends toward over decades — any single day, month or year can and will depart from it.