Weather in Johannesburg in May

Prime time. May is about as good as Johannesburg gets. Highs average 20.4 °C, lows 5.1 °C, and rain falls on 2 days — nothing in the month is working against you.

May ranks 2 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: it never really gets hot: not one day in an average May reaches 30 °C; the day swings 15.3 °C from low to high, which means one bag has to cover both. Across the twenty years measured, the hottest May day reached 27.8 °C and the coldest night fell to -5.7 °C, and the wettest single day dropped 42 mm — roughly 263% of the month's rain in one day.

This is the volatile part. May rainfall has ranged from 0 mm to 49 mm across the twenty years measured — a 49 mm spread around an average of 16 mm. The average is real but almost no individual May looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 7.1 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 54%.

How May sits in the year

The month is on the way down: 2.4 °C cooler than April, with June dropping another 3 °C. The first week and the last are not the same trip. Rain has already shifted: 6 days fewer than April had.

Daylight in May

May sits at the dark end of Johannesburg's year — 10.9 hours of daylight against 13.8 at midsummer, losing 0.5 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

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 May itself the daily swing is 15.3 °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.

May in Johannesburg versus nearby

If Johannesburg is one option among several, the nearby comparison is worth making. Pretoria is close enough to be a coin toss — 3.4 °C warmer, the same number of rain days. Pietermaritzburg is close enough to be a coin toss — 3.4 °C warmer, 3 days more rain.

So: May 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 May.