Climate and Average Weather Year Round in Heidelberg South Africa

In Heidelberg, the summers are long, warm, and partly cloudy and the winters are short, cold, dry, and clear. Over the course of the year, the temperature typically varies from 33°F to 80°F and is rarely below 27°F or above 86°F.

Based on the tourism score, the best times of year to visit Heidelberg for warm-weather activities are from late August to mid November and from mid December to late April.

The warm season lasts for 5.9 months, from September 21 to March 18, with an average daily high temperature above 76°F. The hottest month of the year in Heidelberg is January, with an average high of 79°F and low of 59°F.

The cool season lasts for 2.1 months, from May 29 to August 1, with an average daily high temperature below 67°F. The coldest month of the year in Heidelberg is July, with an average low of 33°F and high of 65°F.

In Heidelberg, 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 Heidelberg begins around March 28 and lasts for 6.3 months, ending around October 5.

The clearest month of the year in Heidelberg is July, during which on average the sky is clear, mostly clear, or partly cloudy 90% of the time.

The cloudier part of the year begins around October 5 and lasts for 5.7 months, ending around March 28.

The cloudiest month of the year in Heidelberg is November, during which on average the sky is overcast or mostly cloudy 36% 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 Heidelberg varies very significantly throughout the year.

The wetter season lasts 5.5 months, from October 12 to March 27, with a greater than 27% chance of a given day being a wet day. The month with the most wet days in Heidelberg is December, with an average of 15.8 days with at least 0.04 inches of precipitation.

The drier season lasts 6.5 months, from March 27 to October 12. The month with the fewest wet days in Heidelberg is July, with an average of 0.5 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Heidelberg is December, with an average of 15.8 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 53% on December 12.

Rainfall

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 of the year. Heidelberg experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 8.2 months, from September 5 to May 11, with a sliding 31-day rainfall of at least 0.5 inches. The month with the most rain in Heidelberg is December, with an average rainfall of 3.6 inches.

The rainless period of the year lasts for 3.8 months, from May 11 to September 5. The month with the least rain in Heidelberg is July, with an average rainfall of 0.1 inches.

The length of the day in Heidelberg varies over the course of the year. In 2024, the shortest day is June 20, with 10 hours, 29 minutes of daylight; the longest day is December 21, with 13 hours, 49 minutes of daylight.

The earliest sunrise is at 5:05 AM on November 30, and the latest sunrise is 1 hour, 50 minutes later at 6:55 AM on July 2. The earliest sunset is at 5:21 PM on June 8, and the latest sunset is 1 hour, 43 minutes later at 7:04 PM on January 12.

Daylight saving time (DST) is not observed in Heidelberg during 2024.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

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 Heidelberg, 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.

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 Heidelberg experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 4.0 months, from July 31 to November 30, with average wind speeds of more than 8.4 miles per hour. The windiest month of the year in Heidelberg is September, with an average hourly wind speed of 10.0 miles per hour.

The calmer time of year lasts for 8.0 months, from November 30 to July 31. The calmest month of the year in Heidelberg is March, with an average hourly wind speed of 6.8 miles per hour.

The predominant average hourly wind direction in Heidelberg varies throughout the year.

The wind is most often from the east for 1.6 months, from January 31 to March 18, with a peak percentage of 37% on February 19. The wind is most often from the north for 3.4 weeks, from March 18 to April 11 and for 5.9 months, from August 3 to January 31, with a peak percentage of 30% on March 26. The wind is most often from the west for 3.7 months, from April 11 to August 3, with a peak percentage of 35% on May 11.

To characterize how pleasant the weather is in Heidelberg throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best times of year to visit Heidelberg for general outdoor tourist activities are from late August to mid November and from mid December to late April, with a peak score in the first week of March.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Heidelberg for hot-weather activities is from mid December to early March, with a peak score in the second week of February.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Heidelberg typically lasts for 9.2 months (280 days), from around August 18 to around May 25, rarely starting before July 24 or after September 10, and rarely ending before April 30 or after June 12.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms in Heidelberg should appear around July 24, only rarely appearing before July 20 or after July 29.

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 4.1 months, from October 21 to February 25, with an average daily incident shortwave energy per square meter above 7.0 kWh. The brightest month of the year in Heidelberg is December, with an average of 7.6 kWh.

The darker period of the year lasts for 2.8 months, from May 7 to August 1, with an average daily incident shortwave energy per square meter below 4.9 kWh. The darkest month of the year in Heidelberg is June, with an average of 4.2 kWh.

For the purposes of this report, the geographical coordinates of Heidelberg are -26.505 deg latitude, 28.359 deg longitude, and 5,003 ft elevation.

The topography within 2 miles of Heidelberg contains significant variations in elevation, with a maximum elevation change of 722 feet and an average elevation above sea level of 5,112 feet. Within 10 miles contains significant variations in elevation (1,444 feet). Within 50 miles contains very significant variations in elevation (2,192 feet).

The area within 2 miles of Heidelberg is covered by grassland (62%) and artificial surfaces (29%), within 10 miles by grassland (70%) and cropland (22%), and within 50 miles by grassland (50%) and cropland (34%).