Weather in Johannesburg, month by month

Warmest month: January, 21.6
Coldest month: July, 9.9
Wettest month: December, 127 mm
Year: 2001-2020

Weather in Port Elizabeth, month by month

Same data, same method, different place.

Your own numbers, worked out on the page.

Across the 2001-2020 normals, the warmest month in Johannesburg is January at 21.6 degrees and the coldest is July at 9.9, a swing of 11.8 degrees over the year. Those are monthly averages for the model cell the city sits in, not readings from a weather station in it.

Rain is heaviest in December, about 127 mm, and lightest in July at roughly 3 mm. Over a full year the cell above Johannesburg collects around 642 mm.

The months whose average sits between 15 and 24 degrees are January, February, March, April, September, October, November and December. That band is this page's own definition of mild and is stated so you can disagree with it rather than guess at it.

Humidity peaks in January at 65 percent, and the windiest month is September at 3 metres per second. Both are monthly means from the same twenty year series as the temperatures.

Rainfall is not spread evenly: 86 per cent of the year total falls in October, November, December, January, February and March.

Every figure here comes from one NASA POWER grid cell, at -26.2, 28.04, covering Johannesburg on the 2001-2020 climatology. One cell, one period and one provider for every month, which is what makes the twelve rows comparable with each other.

The source publishes a monthly mean and, separately, the highest and lowest values it recorded in twenty years. Those extremes are not a typical afternoon or a typical night, so nothing here is quoted as one. This page does not say what the daytime high usually is, because this source cannot say it.

Normals are not a forecast. They describe what twenty years averaged to, and any single year can sit well outside them. They also describe a model grid cell of roughly fifty kilometres rather than a weather station, so a coastal city and the sea beside it share one figure.