ヨハネスブルグの月別の天気

Johannesburg forum threads describe January as genuinely rainy - posters cited an average of nearly 200mm for the month in parts of the city - but consistently emphasized that heavy waterproof gear isn't really necessary, since the typical pattern is a brief, intense afternoon thunderstorm with thunder and lightning that rarely lasts more than an hour or two before clearing. Posters described an umbrella as rarely even used in practice. The daytime heat was called genuinely warm, classic Highveld summer conditions, and the consistent packing advice was light summer clothing suited to hot, sunny mornings with a real but short-lived storm risk each afternoon.

Johannesburg forum regulars call March still genuinely warm — “daytime temperatures well into the 20s...dropping overnight to the low teens” — with the rainy season technically still active but “should be drying up.” The rain pattern that shows up repeatedly: thunderstorms towards the end of the day that cool the evening down, brief rather than all-day. Standard packing leans toward layering for the day-night swing: long pants (zip-offs work well for cool mornings that warm up), a fleece or two, a lightweight waterproof jacket, with shorts still fine for the warm afternoons. Our record: 23.5°C days, 12.7°C nights and 9.8 rain days — warm with real afternoon rain risk, matching the “still rainy season, but easing” read for March specifically.

Regulars sum up the end of April here in a sentence about footwear: mid-twenties by day and still open-toed weather, except in the evenings and the early mornings. Our row is that exactly - 24.2C days falling to 10.8C nights that feel like 9C. April and May are the tolerable part of the Highveld year, cooler than March and with fewer mosquitoes, and the rain is already thinning ahead of a winter they describe as having virtually none between June and September; ours reads 75.9mm across 8.9 days. The figure worth checking is the air at AQI 80. The record: humidity 68 percent, 9.3 hours of sun and a 15 kph wind.

May is winter on the highveld and regulars describe the shape of it exactly: sunny days in the low twenties, nights down to about five with frost possible, and almost no rain, because this is a summer-rainfall region. Our row gives 22.3C reading as 19C and 7.5C reading as 4C, with 21.4mm across 2.9 days on very dry air - 58 percent humidity and a dew point of 3.5C. Layers that come off by mid-morning and go back on at four. Anyone doing an early game drive needs more than they expect. The one cost of clear windless winter air is our AQI at 100, climbing towards the year's peak of 109 in June. The record: 9.6 hours of sun and a 13.9 kph wind.

August is the middle of the Highveld winter and regulars call Johannesburg stunning in it: sunshine almost every day and effectively no rain, which our row confirms at 3.1mm across half a precipitation day. The temperature they describe is not a single number but a place - very warm in the sun, cool to cold in the shade, and something to wrap up in the moment the sun goes. Early mornings are cold and late nights bitingly so, while the days themselves run into the mid-20s. Our row is the arithmetic of that: a 23.4C average high over a 5.9C night that feels like 2C, at 41 percent humidity. The record: 10.1 hours of sun, a 19 kph wind and AQI 88.

South Africa's forum places Johannesburg at its best from mid-September on — genuine spring, warm days without the harsh heat of high summer. Regulars' one consistent tip: evenings still call for a light jacket, the temperature drops faster after sunset than the daytime warmth suggests.

Regulars call this close to the perfect month here, springtime warmth without summer's full intensity, though late in the month marks the real start of the rainy season, sporadic thunderstorms typically arriving in the late afternoon or early evening rather than settling in for the day. Our row backs that warm, increasingly showery read, 28.5C over 11.6C nights feeling 9C, with 61.2mm of rain across 8.8 days and humidity down to 48 percent. Regulars are consistent mornings still run cool enough for a jacket even as afternoons turn genuinely warm, a real day-to-night swing worth packing for. This remains a comfortable month overall for exploring before the full rainy season sets in through the following months. The record: 10.9 hours of sun, a 19.7 kph wind and AQI 69.