Weather in Johannesburg in September

Prime time. September is about as good as Johannesburg gets. Highs average 25.4 °C, lows 7.6 °C, and rain falls on 2 days — nothing in the month is working against you.

September ranks 3 of 12 in Johannesburg. Only August scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain falls on only 2 days, so an itinerary with no wet-weather fallback is a reasonable risk. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: the day swings 17.8 °C from low to high, which means one bag has to cover both. Across the twenty years measured, the hottest September day reached 31.9 °C and the coldest night fell to -3 °C, and the wettest single day dropped 40 mm — roughly 250% of the month's rain in one day.

This is the volatile part. September rainfall has ranged from 0 mm to 64 mm across the twenty years measured — a 64 mm spread around an average of 16 mm. The average is real but almost no individual September looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 10.6 km/h, so the temperature on the page is close to the temperature on your skin, and the air is dry at 39% humidity, which makes the heat far more bearable than the same figure somewhere humid — and dehydrates you faster than you expect.

How September sits in the year

The month is on the way up: 4.4 °C warmer than August, and October adds another 1.6 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short. Rain is the thing that moves: October brings 8 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in September

11.9 hours of daylight, gaining 0.8 hours across the month. That is between Johannesburg's extremes of 13.8 and 10.5 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 25.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage. At 1767 m, altitude is doing as much work here as latitude: thinner air means fierce sun by day and heat that leaves the moment it sets. Within September itself the daily swing is 17.8 °C, so mornings and afternoons need different clothes.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead. If the dates are flexible, April is the trade worth considering — 12 points weaker on weather, and materially quieter.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Johannesburg versus nearby

If Johannesburg is one option among several, the nearby comparison is worth making. Pretoria is the weaker option in September — 3.5 °C warmer, the same number of rain days. Pietermaritzburg is the weaker option in September — within a degree on temperature, 8 days more rain.

So: September is effectively as good as it gets here — 1 points behind August, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Johannesburg

See all twelve months in Johannesburg, or where else to go in September.