Heilbronn weather in September

In September, Heilbronn sees average daytime highs of 19°C and overnight lows near 11°C, with 63 mm of rain across 10.3 wet days and about 12.4 hours of daylight. It is the 4th-warmest and 10th-wettest month of the year here.

Highs ease over the month, from about 21°C in the first days to 17°C by the end. The sky is clear or mostly clear about 25% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 18 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Heilbronn's 3rd-clearest and 9th-windiest month. For the whole year in context, see Heilbronn's year-round climate.

Daytime high
19°
4th warmest
Overnight low
11°
9th coldest
Rainfall
63 mm
10.3 wet days
Daylight
12 h 24 min
6:07 AM – 6:28 PM
Cloud cover
62%
3rd clearest
Wind
9 km/h
9th windiest
Solar energy
3.35 kWh/m²
Travel score
6.0
out of 10
Air quality
Moderate
PM2.5 11.6 µg/m³ · 2019

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 21°C in the first days to 17°C by the end.

A typical September day in Heilbronn reaches about 19°C in the afternoon and slips back to 11°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 14°C and 25°C. Set against its neighbours, September runs about 5°C cooler than August and about 6°C warmer than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12212
22112
32112
42112
52112
62112
72112
82011
92011
102011
112011
122011
132011
142011
151910
161910
171910
181910
191910
201910
211810
221810
231810
24189
25189
26189
27179
28179
29179
30179

How September really feels in Heilbronn

Once humidity and wind are folded in, September averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Heilbronn weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -1°7612.34.48.50.0
Feb / -1°6611.34.39.80.2
Mar10° / 7612.5211.62.0
Apr15° / 5210.40.213.44.2
May19° / 7913.10155.5
Jun22° / 13°6612.2015.96.2
Jul24° / 14°7412.7015.66.5
Aug24° / 14°6211.1014.26.7
Sep19° / 11°6310.3012.46.0
Oct14° / 7211.80.110.53.7
Nov / 7211.61.48.91.1
Dec / 9014.64.78.10.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 25% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 60%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
14555
24555
34456
44456
54456
64258
74357
84258
94258
104258
114159
124159
134159
144159
154159
164159
174159
184060
194060
204060
213961
223961
233961
243763
253763
263565
273565
283367
293367
303169

Chance of precipitation in September

Any precipitation

Heilbronn gets around 63 mm of rain over 10.3 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 36% and peaks near 41% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
135
235
335
435
535
635
735
835
935
1035
1135
1235
1335
1435
1534
1634
1734
1834
1934
2034
2134
2234
2335
2436
2537
2637
2738
2839
2940
3041

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the dry band about 80% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
167258
268257
370246
471236
572235
674224
774224
874224
976213
1076213
1177203
1278202
1379192
1480182
1580182
1681172
1783161
1884151
1984151
2085141
2185141
2286131
2387130
2488120
2588120
2688120
2789110
2889110
2990100
3090100

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 9 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
19calm
29calm
39calm
49calm
59calm
69calm
79calm
89calm
99calm
109calm
1110calm
1210calm
1310calm
1410calm
1510calm
1610calm
179calm
189calm
199calm
209calm
219calm
229calm
239calm
249calm
259calm
2610calm
2710calm
2810calm
2910calm
3010calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 18 min at the start of September to 11 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 108 minutes over September. Sunrise moves from 5:44 AM to 6:28 AM, and sunset from 7:01 PM to 5:57 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.35:447:01
213.25:466:59
313.25:476:57
413.15:496:55
513.05:506:53
613.05:526:50
712.95:536:48
812.95:556:46
912.85:566:44
1012.75:586:42
1112.75:596:39
1212.66:016:37
1312.56:026:35
1412.56:046:33
1512.46:056:30
1612.46:076:28
1712.36:086:26
1812.26:106:24
1912.26:116:21
2012.16:136:19
2112.06:146:17
2212.06:166:15
2311.96:176:13
2411.96:196:10
2511.86:206:08
2611.76:226:06
2711.76:236:04
2811.66:256:01
2911.56:265:59
3011.56:285:57

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 3.35 kWh/m².

For context, solar energy here swings from a low near 0.75 kWh/m² to a high of 5.6 kWh/m² in June across the year — September's 3.35 kWh/m² falls in the middle.

01234151015202530
Solar energy (kWh/m²)Level
14.0Moderate
23.9Moderate
33.9Moderate
43.8Moderate
53.8Moderate
63.8Moderate
73.7Moderate
83.7Moderate
93.6Moderate
103.6Moderate
113.5Moderate
123.5Moderate
133.5Moderate
143.4Moderate
153.4Moderate
163.3Moderate
173.3Moderate
183.3Moderate
193.2Moderate
203.2Moderate
213.1Moderate
223.1Moderate
233.0Moderate
243.0Moderate
252.9Moderate
262.9Moderate
272.8Moderate
282.7Moderate
292.7Moderate
302.6Moderate
Planning a trip in September

Is September a good time to visit Heilbronn?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

6.0
Sightseeing
4th-best month of the year
2.7
Beach & pool
4th-best month of the year

September is a reasonable time to visit Heilbronn for sightseeing.

What to pack for Heilbronn in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Heilbronn sees daytime highs around 19°C and nights near 11°C. Worth packing: rain gear. About 10 days see rain.

rain gear

UV index in Heilbronn in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Heilbronn peaks around July 15 at about 7 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near January 1 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 15UV 7Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar4Moderate
Apr4Moderate
May6High
Jun7High
Jul8Very high
Aug6High
Sep4Moderate
Oct3Moderate
Nov1Low
Dec1Low

Air quality in Heilbronn in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Heilbronn is worst in April — around 15 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (November, 8 µg/m³).

Seasonal pattern from CAMS reanalysis, scaled to Heilbronn's WHO annual average of 11.6 µg/m³.

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodApr 1715 µg/m³Nov 238 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb10Good
Mar13Moderate
Apr15Moderate
May14Moderate
Jun15Moderate
Jul12Moderate
Aug13Moderate
Sep12Good
Oct10Good
Nov8Good
Dec8Good
Location & terrain

Where is Heilbronn?

Heilbronn sits at 49.1°N, 9.2°E, 173 m above sea level, in Germany. The nearest listed city is Neckarsulm, 5.0 km away.

Topography around Heilbronn

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Heilbronn.

Within 3 km, the terrain around Heilbronn has only modest variations in elevation — a maximum elevation change of 181 m around an average of 196 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 416 m; within 80 km, large variations in elevation — a maximum elevation change of 910 m.

The land around Heilbronn is covered by artificial surfaces (43%) and trees (34%) within 3 km, cropland (37%) and trees (31%) within 16 km, and trees (47%) and cropland (28%) within 80 km.

3 km
181 m
16 km
416 m
80 km
910 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Neckarsulm 5.0 km · Brackenheim 13 km · Bad Rappenau 14 km · Öhringen 22 km · Eppingen 22 km · Marbach am Neckar 22 km · Sachsenheim 23 km · Bietigheim-Bissingen 23 km

Germany travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 80% of US
price level, 2025
GDP per capita
$60,496
2025
Happiness
6.9 / 10
World Happiness, 2025
Safe drinking water
100%
of population, 2024
Homicide rate
0.9
per 100k, 2023
Road deaths
3.8
per 100k/yr, 2019
Income group
High
World Bank
English
Very high
EF EPI 615
Religion
none 44%Roman Catholic 25%Protestant 23%other 5%

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 Heilbronn (49.1399°, 9.2205°, elevation 173 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).