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Average Weather in January in Johannesburg South Africa

In Johannesburg, the month of January is characterized by essentially constant daily high temperatures, with daily highs around 78°F throughout the month, rarely exceeding 85°F or dropping below 70°F. The highest daily average high temperature is 78°F on January 1.

Daily low temperatures are around 59°F, rarely falling below 55°F or exceeding 63°F. The highest daily average low temperature is 59°F on January 22.

For reference, on January 1, the hottest day of the year, temperatures in Johannesburg typically range from 59°F to 78°F, while on July 5, the coldest day of the year, they range from 36°F to 61°F.

Average High and Low Temperature in January

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on January. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature in January

Average Hourly Temperature in January in Johannesburg12 AM4 AM8 AM12 PM4 PM8 PM12 AM181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930303131DecFebcoolcomfortablewarm
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < chilly < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Clouds

The month of January in Johannesburg experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 33% throughout the month.

The clearest day of the month is January 31, with clear, mostly clear, or partly cloudy conditions 68% of the time.

For reference, on November 25, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 38%, while on July 21, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.

Cloud Cover in January

The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Johannesburg, the chance of a wet day over the course of January is gradually decreasing, starting the month at 51% and ending it at 48%.

For reference, the year's highest daily chance of a wet day is 55% on December 17, and its lowest chance is 1% on July 8.

Probability of Precipitation in January

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during January in Johannesburg is essentially constant, remaining about 3.8 inches throughout, and rarely exceeding 7.5 inches or falling below 1.4 inches.

The highest average 31-day accumulation is 3.9 inches on January 17.

Average Monthly Rainfall in January

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

Over the course of January in Johannesburg, the length of the day is gradually decreasing. From the start to the end of the month, the length of the day decreases by 26 minutes, implying an average daily decrease of 53 seconds, and weekly decrease of 6 minutes, 11 seconds.

The shortest day of the month is January 31, with 13 hours, 18 minutes of daylight and the longest day is January 1, with 13 hours, 45 minutes of daylight.

Hours of Daylight and Twilight in January

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise of the month in Johannesburg is 5:18 AM on January 1 and the latest sunrise is 23 minutes later at 5:41 AM on January 31.

The latest sunset is 7:05 PM on January 11 and the earliest sunset is 5 minutes earlier at 7:00 PM on January 31.

Daylight saving time is not observed in Johannesburg during 2017.

For reference, on December 21, the longest day of the year, the Sun rises at 5:12 AM and sets 13 hours, 47 minutes later, at 6:59 PM, while on June 21, the shortest day of the year, it rises at 6:54 AM and sets 10 hours, 30 minutes later, at 5:24 PM.

Sunrise & Sunset with Twilight in January

The solar day over the course of January. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Humidity

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 chance that a given day will be muggy in Johannesburg is essentially constant during January, remaining around 1% throughout.

For reference, on February 23, the muggiest day of the year, there are muggy conditions 2% of the time, while on April 13, the leasy muggy day of the year, there are muggy conditions 0% of the time.

Humidity Comfort Levels in January

The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

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 is essentially constant during January, remaining within 0.1 miles per hour of 3.8 miles per hour throughout.

For reference, on September 25, the windiest day of the year, the daily average wind speed is 5.2 miles per hour, while on March 31, the calmest day of the year, the daily average wind speed is 3.4 miles per hour.

Average Wind Speed in January

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.
The hourly average wind direction in Johannesburg throughout January is predominantly from the north, with a peak proportion of 49% on January 1.

Wind Direction in January

Wind Direction in January in JohannesburgNE0%20%40%60%80%100%181522291122334455667788991010111112121313141415151616171718181919202021212222232324242525262627272828292930303131DecFebeastnorthwestsouth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Solar Energy

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 in Johannesburg is essentially constant during January, remaining within 0.1 kWh of 7.5 kWh throughout.

Average Daily Incident Shortwave Solar Energy in January

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

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 only modest variations in elevation (1,230 feet). Within 50 miles contains very significant 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%).

Data Sources

This report illustrates the typical weather in Johannesburg year round, 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).

Other Data

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 .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.