Climate and average weather in Heilbron
In Heilbron, the summers are warm, wet, and partly cloudy and the winters are mild and clear.
Over the course of the year, the temperature in Heilbron typically varies from 3°C to 27°C, and is rarely below -1°C or above 32°C. January is the hottest month of the year, while June is the coldest.
Based on the travel score, the best time of year to visit Heilbron for warm-weather activities is from late March to mid October.
- Hottest
- Jan
- 27°
- Coldest
- Jun
- 3°
- Wettest
- Dec
- 139 mm
- Driest
- Jul
- 6 mm
- Rain / yr
- 717 mm
- 96 wet days
- Daylight
- 10.3–13.7 h
- shortest–longest
- Elevation
- 1,539 m
- 27.3°S
- Clearest
- Jul
- 13% cloud
Heilbron is town in the Free State, South Africa.
- Founded
- 1872
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Heilbron weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around late March to mid October.
Temperature through the year
Daily average highs and lows in Heilbron, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 6.3 months, from September 15 to March 25, with daily high temperatures above 25°C. The hottest month of the year in Heilbron is January, with an average high of 27°C and low of 16°C.
The cool season lasts 2.2 months, from May 29 to August 3, with daily high temperatures below 19°C. The coldest month of the year in Heilbron is June, with an average low of 3°C and high of 18°C.
Days typically run about 13°C warmer than nights, with the widest day–night swing (around 15°C) in July.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 27 | 27 | 25 | 23 | 21 | 18 | 18 | 21 | 25 | 26 | 26 | 27 |
| Avg low (°C) | 16 | 16 | 14 | 11 | 7 | 3 | 3 | 6 | 10 | 13 | 14 | 15 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 27 | 16 |
| Feb | 27 | 16 |
| Mar | 25 | 14 |
| Apr | 23 | 11 |
| May | 21 | 7 |
| Jun | 18 | 3 |
| Jul | 18 | 3 |
| Aug | 21 | 6 |
| Sep | 25 | 10 |
| Oct | 26 | 13 |
| Nov | 26 | 14 |
| Dec | 27 | 15 |
How hot and cold Heilbron really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the coldest nights, wind chill pulls the feels-like down to about -0°C (around July 3), with roughly 30 freezing days a year (feels-like at or below 0°C), worst in July.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°C) | 27 | 27 | 25 | 23 | 21 | 18 | 18 | 21 | 25 | 26 | 26 | 27 |
| Air high (°C) | 27 | 27 | 25 | 23 | 21 | 18 | 18 | 21 | 25 | 26 | 26 | 27 |
| Feels-like low (°C) | 16 | 16 | 14 | 10 | 4 | 0 | 0 | 3 | 9 | 12 | 14 | 15 |
| Air low (°C) | 16 | 16 | 14 | 11 | 7 | 3 | 3 | 6 | 10 | 13 | 14 | 15 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 27 | 27 | 16 | 16 |
| Feb | 27 | 27 | 16 | 16 |
| Mar | 25 | 25 | 14 | 14 |
| Apr | 23 | 23 | 10 | 11 |
| May | 21 | 21 | 4 | 7 |
| Jun | 18 | 18 | 0 | 3 |
| Jul | 18 | 18 | 0 | 3 |
| Aug | 21 | 21 | 3 | 6 |
| Sep | 25 | 25 | 9 | 10 |
| Oct | 26 | 26 | 12 | 13 |
| Nov | 26 | 26 | 14 | 14 |
| Dec | 27 | 27 | 15 | 15 |
Average hourly temperature in Heilbron
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on January afternoons, near 27°C, and coldest before dawn in June, near 3°C.
Heilbron weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 27° / 16° | 124 | 15 | 13.5 | 5.9 |
| Feb | 27° / 16° | 87 | 12.6 | 13 | 6.2 |
| Mar | 25° / 14° | 81 | 11.1 | 12.2 | 6.9 |
| Apr | 23° / 11° | 43 | 6.9 | 11.4 | 7.7 |
| May | 21° / 7° | 19 | 3.1 | 10.7 | 8.1 |
| Jun | 18° / 3° | 10 | 1.7 | 10.3 | 7.8 |
| Jul | 18° / 3° | 6 | 1.1 | 10.5 | 7.9 |
| Aug | 21° / 6° | 15 | 2.4 | 11 | 8.4 |
| Sep | 25° / 10° | 20 | 3.2 | 11.8 | 8.6 |
| Oct | 26° / 13° | 76 | 9.8 | 12.7 | 7.1 |
| Nov | 26° / 14° | 98 | 12.5 | 13.3 | 6.4 |
| Dec | 27° / 15° | 139 | 16.6 | 13.7 | 5.8 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Heilbron gets about 717 mm of precipitation a year. On a typical day the chance of rain is some rain, but that rises and falls sharply with the seasons.
The wetter season lasts 5.8 months, from around Oct 9 to Apr 3, peaking in December at about 53% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jul 11.
December is the wettest month by volume, with 139 mm over about 17 wet days; July is the driest, with 6 mm.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 49 | 45 | 36 | 23 | 10 | 6 | 4 | 8 | 11 | 31 | 43 | 52 |
| Rain days | 15 | 13 | 11 | 7 | 3 | 2 | 1 | 2 | 3 | 10 | 13 | 17 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 49 | 15 |
| Feb | 45 | 13 |
| Mar | 36 | 11 |
| Apr | 23 | 7 |
| May | 10 | 3 |
| Jun | 6 | 2 |
| Jul | 4 | 1 |
| Aug | 8 | 2 |
| Sep | 11 | 3 |
| Oct | 31 | 10 |
| Nov | 43 | 13 |
| Dec | 52 | 17 |
Monthly rainfall
Over a full year, Heilbron collects about 717 mm of rain across 96 wet days — roughly 60 mm in an average month.
It doesn’t fall evenly. December is the wettest month with 139 mm, while July is the driest at just 6 mm. The three wettest months alone bring about 50% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 124 | 87 | 81 | 43 | 19 | 10 | 6 | 15 | 20 | 76 | 98 | 139 |
| Rain days | 15 | 13 | 11 | 7 | 3 | 2 | 1 | 2 | 3 | 10 | 13 | 17 |
| Rainfall (mm) | Rain days | |
|---|---|---|
| Jan | 124 | 15 |
| Feb | 87 | 13 |
| Mar | 81 | 11 |
| Apr | 43 | 7 |
| May | 19 | 3 |
| Jun | 10 | 2 |
| Jul | 6 | 1 |
| Aug | 15 | 2 |
| Sep | 20 | 3 |
| Oct | 76 | 10 |
| Nov | 98 | 13 |
| Dec | 139 | 17 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Heilbron, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around April 19 and lasts for 5.6 months, ending around October 4. The clearest month is July, when the sky is clear, mostly clear, or partly cloudy 93% of the time on average.
The cloudier part of the year begins around October 5 and lasts for 6.4 months, ending around April 18. The cloudiest month is December, when it is overcast or mostly cloudy 39% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 64 | 68 | 72 | 76 | 85 | 91 | 93 | 89 | 83 | 71 | 62 | 61 |
| Cloudier (%) | 36 | 32 | 28 | 24 | 15 | 9 | 7 | 11 | 17 | 29 | 38 | 39 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 64 | 36 |
| Feb | 68 | 32 |
| Mar | 72 | 28 |
| Apr | 76 | 24 |
| May | 85 | 15 |
| Jun | 91 | 9 |
| Jul | 93 | 7 |
| Aug | 89 | 11 |
| Sep | 83 | 17 |
| Oct | 71 | 29 |
| Nov | 62 | 38 |
| Dec | 61 | 39 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around January 1, brings about 13 h 42 min of light; the shortest, around June 7, only 10 h 18 min — a swing of roughly 3 h 24 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 13.5 | 13.0 | 12.2 | 11.4 | 10.7 | 10.3 | 10.5 | 11.0 | 11.8 | 12.7 | 13.3 | 13.7 |
| Sunrise (AM) | 5:31 | 5:54 | 6:12 | 6:28 | 6:45 | 7:00 | 7:01 | 6:41 | 6:07 | 5:33 | 5:12 | 5:13 |
| Sunset (PM) | 7:04 | 6:52 | 6:24 | 5:49 | 5:24 | 5:17 | 5:27 | 5:43 | 5:58 | 6:13 | 6:34 | 6:56 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 13.5 | 5:31 | 7:04 |
| Feb | 13.0 | 5:54 | 6:52 |
| Mar | 12.2 | 6:12 | 6:24 |
| Apr | 11.4 | 6:28 | 5:49 |
| May | 10.7 | 6:45 | 5:24 |
| Jun | 10.3 | 7:00 | 5:17 |
| Jul | 10.5 | 7:01 | 5:27 |
| Aug | 11.0 | 6:41 | 5:43 |
| Sep | 11.8 | 6:07 | 5:58 |
| Oct | 12.7 | 5:33 | 6:13 |
| Nov | 13.3 | 5:12 | 6:34 |
| Dec | 13.7 | 5:13 | 6:56 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Heilbron averages about 18 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 11 and 26 days.
The sunnier stretch runs 5.4 months, from around Apr 19 to Sep 30. The sunniest month is July, with roughly 26 sunny days (brilliant).
The greyest month is December, down near 11 sunny days — about 56% fewer than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 12 | 12 | 15 | 18 | 23 | 25 | 26 | 25 | 21 | 16 | 13 | 12 |
| Sky | Mixed | Mixed | Mixed | Bright | Bright | Brilliant | Brilliant | Brilliant | Bright | Bright | Mixed | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 12 | Mixed |
| Feb | 12 | Mixed |
| Mar | 15 | Mixed |
| Apr | 18 | Bright |
| May | 23 | Bright |
| Jun | 25 | Brilliant |
| Jul | 26 | Brilliant |
| Aug | 25 | Brilliant |
| Sep | 21 | Bright |
| Oct | 16 | Bright |
| Nov | 13 | Mixed |
| Dec | 12 | Mixed |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In Heilbron, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 3.2 months, from around December 11 to March 18. The muggiest month is January, when the air feels humid, muggy or worse about 27% of the time.
The most comfortable stretch runs from around March 19 to December 10, and April is the most comfortable month — the air is dry or comfortable 100% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 27 | 29 | 53 | 92 | 100 | 100 | 100 | 100 | 100 | 92 | 73 | 43 |
| Comfortable (%) | 46 | 46 | 39 | 7 | 0 | 0 | 0 | 0 | 0 | 8 | 25 | 47 |
| Humid (%) | 27 | 25 | 8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 10 |
| Dry (%) | Comfortable (%) | Humid (%) | |
|---|---|---|---|
| Jan | 27 | 46 | 27 |
| Feb | 29 | 46 | 25 |
| Mar | 53 | 39 | 8 |
| Apr | 92 | 7 | 0 |
| May | 100 | 0 | 0 |
| Jun | 100 | 0 | 0 |
| Jul | 100 | 0 | 0 |
| Aug | 100 | 0 | 0 |
| Sep | 100 | 0 | 0 |
| Oct | 92 | 8 | 0 |
| Nov | 73 | 25 | 2 |
| Dec | 43 | 47 | 10 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Heilbron is typically calm, near 11 km/h, and varies little with the seasons.
The windier part of the year lasts 5.0 months, from around Aug 6 to Jan 5. The windiest month is September, averaging about 13 km/h (light breeze).
The calmer part of the year runs from around Jan 6 to Aug 5, with May the calmest month at about 10 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 11 | 11 | 10 | 10 | 10 | 10 | 10 | 12 | 13 | 13 | 13 | 12 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | light breeze | light breeze | light breeze | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 11 | calm |
| Feb | 11 | calm |
| Mar | 10 | calm |
| Apr | 10 | calm |
| May | 10 | calm |
| Jun | 10 | calm |
| Jul | 10 | calm |
| Aug | 12 | calm |
| Sep | 13 | light breeze |
| Oct | 13 | light breeze |
| Nov | 13 | light breeze |
| Dec | 12 | calm |
Hazard calendar for Heilbron
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Heilbron's rainy season runs October–March, when most of the year's rain falls.
Best time to visit Heilbron
To characterize how pleasant the weather is in Heilbron throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around early April, Heilbron is still near the start of its best-weather window — great conditions with the peak-season crowds not yet at full swing.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 18°C and 28°C. Based on this score, the best time of year to visit Heilbron for general outdoor tourist activities is from late March to mid October, with a peak score in the first week of September.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 5.9 | 6.2 | 6.9 | 7.7 | 8.1 | 7.9 | 7.9 | 8.4 | 8.6 | 7.2 | 6.3 | 5.8 |
| Rating | good | good | good | ideal | ideal | ideal | ideal | ideal | ideal | good | good | good |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 5.9 | good |
| Feb | 6.2 | good |
| Mar | 6.9 | good |
| Apr | 7.7 | ideal |
| May | 8.1 | ideal |
| Jun | 7.9 | ideal |
| Jul | 7.9 | ideal |
| Aug | 8.4 | ideal |
| Sep | 8.6 | ideal |
| Oct | 7.2 | good |
| Nov | 6.3 | good |
| Dec | 5.8 | good |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best times of year to visit Heilbron for hot-weather activities run from early February to mid April and again from late August to late November, with a peak score in the third week of September.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Heilbron, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around January (highs near 27°C), the essentials are light clothes, rain gear and sun protection. In the cold season around June (highs near 18°C), pack a warm layer.
In January, Heilbron sees daytime highs around 27°C and nights near 16°C. Pack rain gear and sun protection. Worth having: light clothes. About 15 days see rain.
UV index (midday) in Heilbron by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in Heilbron peaks around January 14 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 20 at about 5 (high).
The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 15 | 13 | 11 | 8 | 6 | 5 | 5 | 7 | 9 | 10 | 12 | 14 |
| Level | Extreme | Extreme | Extreme | Very high | High | Moderate | High | Very high | Very high | Extreme | Extreme | Extreme |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 15 | Extreme |
| Feb | 13 | Extreme |
| Mar | 11 | Extreme |
| Apr | 8 | Very high |
| May | 6 | High |
| Jun | 5 | Moderate |
| Jul | 5 | High |
| Aug | 7 | Very high |
| Sep | 9 | Very high |
| Oct | 10 | Extreme |
| Nov | 12 | Extreme |
| Dec | 14 | Extreme |
Average hourly UV index in Heilbron
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in January the burn window is concentrated in the middle of the day: about 9 hours a day reach index 3 (protection recommended), and 7 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 9 | 8.5 | 8 | 6.5 | 5.5 | 4.5 | 5 | 6 | 7 | 8 | 8.5 | 9 |
| UV ≥ 6 (h/day) | 7 | 6.5 | 5.5 | 4 | 1.5 | 0 | 0 | 3 | 4.5 | 5.5 | 6 | 7 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 9 | 7 |
| Feb | 8.5 | 6.5 |
| Mar | 8 | 5.5 |
| Apr | 6.5 | 4 |
| May | 5.5 | 1.5 |
| Jun | 4.5 | 0 |
| Jul | 5 | 0 |
| Aug | 6 | 3 |
| Sep | 7 | 4.5 |
| Oct | 8 | 5.5 |
| Nov | 8.5 | 6 |
| Dec | 9 | 7 |
Air quality in Heilbron by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in Heilbron is worst in July — around 103 µg/m³ PM2.5 (unhealthy), about 4.4× the cleanest month (January, 24 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 24 | 32 | 48 | 64 | 88 | 100 | 103 | 83 | 65 | 44 | 31 | 25 |
| Level | Moderate | Moderate | Poor | Unhealthy | Unhealthy | Unhealthy | Unhealthy | Unhealthy | Unhealthy | Poor | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 24 | Moderate |
| Feb | 32 | Moderate |
| Mar | 48 | Poor |
| Apr | 64 | Unhealthy |
| May | 88 | Unhealthy |
| Jun | 100 | Unhealthy |
| Jul | 103 | Unhealthy |
| Aug | 83 | Unhealthy |
| Sep | 65 | Unhealthy |
| Oct | 44 | Poor |
| Nov | 31 | Moderate |
| Dec | 25 | Moderate |
Growing season
Heilbron is mild enough that a frost-free day stays more likely than not even in midwinter. Nights are reliably above freezing from about July 26 to June 9 (319 days); outside that window a hard frost is an occasional risk.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 100 | 100 | 100 | 100 | 99 | 88 | 85 | 97 | 100 | 100 | 100 | 100 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 21 | 25 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 100 | 0 |
| Feb | 100 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 99 | 0 |
| Jun | 88 | 21 |
| Jul | 85 | 25 |
| Aug | 97 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 100 | 0 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Heilbron banks about 2,561 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around January.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 357 | 314 | 303 | 206 | 110 | 16 | 13 | 101 | 215 | 283 | 302 | 342 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 357 |
| Feb | 314 |
| Mar | 303 |
| Apr | 206 |
| May | 110 |
| Jun | 16 |
| Jul | 13 |
| Aug | 101 |
| Sep | 215 |
| Oct | 283 |
| Nov | 302 |
| Dec | 342 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Heilbron receives about 5.6 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 3.8 and 7.1 kWh/m².
The brighter stretch of the year lasts 6.4 months, from around Sep 3 to Mar 16. The brightest month is December, averaging about 7.1 kWh/m² (intense).
The dimmest month is June, down near 3.8 kWh/m² — roughly 46% less than the December peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 6.8 | 6.4 | 5.7 | 4.8 | 4.2 | 3.8 | 4.1 | 4.9 | 6.0 | 6.6 | 7.0 | 7.1 |
| Level | Intense | Intense | Bright | Bright | Bright | Moderate | Bright | Bright | Intense | Intense | Intense | Intense |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 6.8 | Intense |
| Feb | 6.4 | Intense |
| Mar | 5.7 | Bright |
| Apr | 4.8 | Bright |
| May | 4.2 | Bright |
| Jun | 3.8 | Moderate |
| Jul | 4.1 | Bright |
| Aug | 4.9 | Bright |
| Sep | 6.0 | Intense |
| Oct | 6.6 | Intense |
| Nov | 7.0 | Intense |
| Dec | 7.1 | Intense |
Where is Heilbron?
Heilbron sits at 27.3°S, 28.0°E, 1,539 m above sea level, in South Africa. The nearest listed city is Koppies, 39 km away.
Topography around Heilbron
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Heilbron.
Within 3 km, the terrain around Heilbron has only modest variations in elevation — a maximum elevation change of 83 m around an average of 1,555 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 268 m; within 80 km, significant variations in elevation — a maximum elevation change of 455 m.
The land around Heilbron is covered by grassland (56%) and cropland (22%) within 3 km, grassland (51%) and cropland (47%) within 16 km, and grassland (56%) and cropland (40%) within 80 km.
South Africa travel facts
- Travel advisory
- Level 2
- Exercise Increased Caution
- Power plugs
- Type C / M / N
- 230 V · 50 Hz
- Prices
- ≈ 41% of US
- price level, 2025
- GDP per capita
- $6,598
- 2025
- Happiness
- 5.0 / 10
- World Happiness, 2025
- Safe drinking water
- 68%
- of population, 2024
- Homicide rate
- 43.7
- per 100k, 2022
- Road deaths
- 22.2
- per 100k/yr, 2019
- Income group
- Upper middle
- World Bank
- English
- Very high
- EF EPI 602
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Heilbron (-27.2812°, 27.9709°, elevation 1,539 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).