Average Weather in Johannesburg South Africa
In Johannesburg, the temperature typically varies from 36°F to 78°F over the course of the year, and is rarely below 30°F or above 85°F.
The warm season lasts for 5.7 months, from September 26 to March 18, with an average daily high temperature above 75°F. The hottest day of the year is January 1, with an average high of 78°F and low of 59°F.
The cool season lasts for 2.2 months, from May 27 to August 3, with an average daily high temperature below 65°F. The coldest day of the year is July 5, with an average low of 36°F and high of 61°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature
The length of the day in Johannesburg varies over the course of the year. In 2017, the shortest day is June 21, with 10 hours, 30 minutes of daylight; the longest day is December 21, with 13 hours, 47 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:07 AM on November 30, and the latest sunrise is 1 hour, 49 minutes later at 6:56 AM on July 2. The earliest sunset is at 5:23 PM on June 8, and the latest sunset is 1 hour, 42 minutes later at 7:05 PM on January 11.
Daylight saving time (DST) is not observed in Johannesburg during 2017.
Sunrise & Sunset with Twilight
In Johannesburg, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Johannesburg begins around March 29 and lasts for 6.3 months, ending around October 8. On July 21, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 92% of the time, and overcast or mostly cloudy 8% of the time.
The cloudier part of the year begins around October 8 and lasts for 5.7 months, ending around March 29. On November 25, the cloudiest day of the year, the sky is overcast or mostly cloudy 38% of the time, and clear, mostly clear, or partly cloudy 62% of the time.
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Johannesburg varies very significantly throughout the year.
The wetter season lasts 5.4 months, from October 17 to March 30, with a greater than 28% chance of a given day being a wet day. The chance of a wet day peaks at 55% on December 17.
The drier season lasts 6.6 months, from March 30 to October 17. The smallest chance of a wet day is 1% on July 8.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 55% on December 17.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day in the year. Johannesburg experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 8.3 months, from September 6 to May 15, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around January 17, with an average total accumulation of 3.9 inches.
The rainless period of the year lasts for 3.7 months, from May 15 to September 6. The least rain falls around July 14, with and average total accumulation of 0.1 inches.
Average Monthly Rainfall
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
The perceived humidity level in Johannesburg, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 1% of 1% throughout.
Humidity Comfort Levels
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.
The average hourly wind speed in Johannesburg experiences mildly seasonal variation over the course of the year.
The windier part of the year lasts for 4.1 months, from July 29 to December 2, with average wind speeds of more than 4.3 miles per hour. The windiest day of the year is September 25, with an average hourly wind speed of 5.2 miles per hour.
The calmer time of year lasts for 7.9 months, from December 2 to July 29. The calmest day of the year is March 31, with an average hourly wind speed of 3.4 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Johannesburg varies throughout the year.
The wind is most often from the north for 1.7 months, from March 3 to April 24 and for 7.4 months, from June 30 to February 10, with a peak percentage of 53% on December 10. The wind is most often from the west for 1.1 months, from April 24 to May 28, with a peak percentage of 31% on May 12. The wind is most often from the south for 1.1 months, from May 28 to June 30, with a peak percentage of 30% on June 5.
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.
The brighter period of the year lasts for 4.2 months, from October 19 to February 26, with an average daily incident shortwave energy per square meter above 7.0 kWh. The brightest day of the year is December 30, with an average of 7.7 kWh.
The darker period of the year lasts for 2.8 months, from May 7 to August 2, with an average daily incident shortwave energy per square meter below 4.9 kWh. The darkest day of the year is June 21, with an average of 4.2 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Johannesburg are -26.202 deg latitude, 28.044 deg longitude, and 5,646 ft elevation.
The topography within 2 miles of Johannesburg contains only modest variations in elevation, with a maximum elevation change of 440 feet, and an average elevation above sea level of 5,705 feet. Within 10 miles contains very significant variations in elevation (1,230 feet). Within 50 miles contains large variations in elevation (2,851 feet).
The area within 2 miles of Johannesburg is covered by artificial surfaces (99%), within 10 miles by artificial surfaces (76%) and grassland (17%), and within 50 miles by grassland (44%) and cropland (30%).
This report illustrates the typical weather in Johannesburg, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Johannesburg.
For each station, the records are corrected for the elevation difference between that station and Johannesburg according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Johannesburg is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Johannesburg and a given station.
The stations contributing to this reconstruction are: Rand Airport (65%, 7 kilometers, northwest), O.R. Tambo International Airport (27%, 21 kilometers, east), and Vereeniging (8%, 41 kilometers, south).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for aiports and weather stations are provided by AskGeo.com .