Weather in Johannesburg

January is the warmest month (average 21.8°C, high 28.4°C) and July is the coolest (average 11.0°C, low 2.9°C). That 10.8°C swing in monthly averages is the first thing to plan around in Johannesburg.

Rain is rainy season runs from November to March, inside an annual total of 642 mm. The wettest month is December at 127 mm; the driest is July at 3 mm. Johannesburg is in South Africa at 26.2°S. The 2001–2020 NASA POWER daily record describes a Mediterranean pattern: dry summers and wetter winters. On this site the months that score closest to a 22°C day, lighter rain, and moderate humidity are January, September, and December.

Hot and cool months in Johannesburg

Johannesburg has a 10.8°C gap between its coolest monthly average (11.0°C in July) and its warmest (21.8°C in January). That is a southern-hemisphere pattern.

Mean high across all twelve months is 25.2°C and mean low is 10.2°C. These are 20-year grid averages, so a city station can read a few degrees warmer or cooler.

When Johannesburg gets wet

The rainy season in Johannesburg starts in November and ends in March (November, December, January, February, and March). December is the core of it at 127 mm. July is the other extreme, with 3 mm.

A rainy day here is a day with at least 1 mm in the NASA POWER series. December averages 20 such days; July averages 1.

The calendar in Johannesburg

January is the warmest month. Afternoon highs average 28.4°C and nights settle near 15.3°C, with 123 mm of rain. The year bottoms out in July. Plan for 2.9°C at night and 19.0°C in the afternoon. August: 22.5°C high, 5.5°C low, 7 mm rain, 44% humidity.

In September, Johannesburg averages 26.9°C by day and 9.1°C at night, with 16 mm of rain. December is the wettest month — 127 mm and 20 rainy days, with 63% humidity.

Best months to visit Johannesburg

The three months with the highest comfort score are January, September, and December: January (21.8°C average, 123 mm, 65% humidity); September (18.0°C average, 16 mm, 39% humidity); December (21.7°C average, 127 mm, 63% humidity). Those months sit across the year end, so they are listed in season order rather than January-to-December. The score rewards averages near 22°C, lower rainfall, and humidity near 60%. It is a climate score, not a festival or price calendar.

If you want the rainy season itself — fewer crowds, greener landscape, heavier rain — aim at November–March instead of the score.

How Johannesburg compares inside South Africa

Soweto is about 20 km away: Johannesburg is about as warm as Soweto at the hot peak and 56 mm wetter over the year than Soweto. Soweto’s wettest month is December (118 mm) versus December here.

Pretoria is about 53 km away: Johannesburg is 2.7°C cooler than Pretoria in its hottest month and 71 mm wetter over the year than Pretoria. Pretoria’s wettest month is January (115 mm) versus December here.

Durban is about 501 km away: Johannesburg is 3.2°C cooler than Durban in its hottest month and 245 mm drier over the year than Durban. Durban’s wettest month is November (122 mm) versus December here.