Welwyn Garden City weather in September

In September, Welwyn Garden City sees average daytime highs of 18°C and overnight lows near 11°C, with 49 mm of rain across 9.5 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 19°C in the first days to 17°C by the end. The sky is clear or mostly clear about 14% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 24 min at the start of September to 11 h 24 min by month's end. Set against the rest of the year, September is Welwyn Garden City's 4th-clearest and 9th-windiest month. For the whole year in context, see Welwyn Garden City's year-round climate.

Daytime high: 18°; 4th warmest
Overnight low: 11°; 9th coldest
Rainfall: 49 mm; 9.5 wet days
Daylight: 12 h 24 min; 5:43 AM – 6:07 PM
Cloud cover: 70%; 4th clearest
Wind: 14 km/h; 9th windiest
Solar energy: 2.99 kWh/m²
Travel score: 5.7; out of 10

Welwyn Garden City is garden city and new town in Hertfordshire, England.

Founded: 1920

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

← August Welwyn Garden City year-round climate October →Best places to visit in September

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 19°C in the first days to 17°C by the end.

A typical September day in Welwyn Garden City reaches about 18°C in the afternoon and slips back to 11°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 15°C and 22°C. Set against its neighbours, September runs about 3°C cooler than August and about 4°C warmer than October.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Avg high (°C)	20	20	20	19	19	19	19	19	19	19	19	19	19	18	18	18	18	18	18	18	18	18	17	17	17	17	17	17	17	16
Avg low (°C)	12	12	12	12	12	12	11	11	11	11	11	11	11	11	11	11	11	11	11	11	10	10	10	10	10	10	10	10	10	10

	Avg high (°C)	Avg low (°C)
1	20	12
2	20	12
3	20	12
4	19	12
5	19	12
6	19	12
7	19	11
8	19	11
9	19	11
10	19	11
11	19	11
12	19	11
13	19	11
14	18	11
15	18	11
16	18	11
17	18	11
18	18	11
19	18	11
20	18	11
21	18	10
22	18	10
23	17	10
24	17	10
25	17	10
26	17	10
27	17	10
28	17	10
29	17	10
30	16	10

How September really feels in Welwyn Garden City

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

heat index over the day's high

Days feeling ≤ 0°C

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.

Welwyn Garden City 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.

Month	High / Low (°C)	Rainfall (mm)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	7° / 2°	53	11	0.9	8.1	0.9
Feb	8° / 2°	43	9.7	1.2	9.6	1.1
Mar	10° / 4°	43	10.3	0.7	11.5	2.2
Apr	13° / 5°	50	11.2	0.2	13.6	3.5
May	16° / 8°	54	10.2	0	15.4	4.9
Jun	19° / 11°	58	10.4	0	16.4	5.8
Jul	21° / 13°	57	11	0	16	6.3
Aug	21° / 13°	62	10.8	0	14.4	6.2
Sep	18° / 11°	49	9.5	0	12.4	5.7
Oct	14° / 8°	58	10.7	0	10.4	4.0
Nov	10° / 5°	60	10.7	0.2	8.6	2.2
Dec	8° / 3°	56	11.2	1.1	7.6	1.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 14% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 70%.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Clearer (%)	33	33	33	33	33	32	32	33	32	32	32	30	31	30	30	29	29	28	27	27	27	27	27	27	27	26	27	27	27	28
Cloudier (%)	67	67	67	67	67	68	68	67	68	68	68	70	69	70	70	71	71	72	73	73	73	73	73	73	73	74	73	73	73	72

	Clearer (%)	Cloudier (%)
1	33	67
2	33	67
3	33	67
4	33	67
5	33	67
6	32	68
7	32	68
8	33	67
9	32	68
10	32	68
11	32	68
12	30	70
13	31	69
14	30	70
15	30	70
16	29	71
17	29	71
18	28	72
19	27	73
20	27	73
21	27	73
22	27	73
23	27	73
24	27	73
25	27	73
26	26	74
27	27	73
28	27	73
29	27	73
30	28	72

Chance of precipitation in September

Any precipitation

Welwyn Garden City gets around 49 mm of rain over 9.5 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 32% and peaks near 38% on the wettest days. The odds climb toward the end of the month.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Rain chance (%)	30	29	29	29	29	29	29	29	30	30	30	30	30	30	30	31	31	32	32	32	33	33	34	35	35	36	36	37	37	38

	Rain chance (%)
1	30
2	29
3	29
4	29
5	29
6	29
7	29
8	29
9	30
10	30
11	30
12	30
13	30
14	30
15	30
16	31
17	31
18	32
19	32
20	32
21	33
22	33
23	34
24	35
25	35
26	36
27	36
28	37
29	37
30	38

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 77% of days. It rarely turns muggy — the humid and sticky bands barely register.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Dry (%)	68	69	70	71	72	72	73	74	74	75	76	76	77	78	78	79	80	80	79	80	80	79	79	80	81	81	82	82	83	83
Comfortable (%)	27	26	26	25	24	24	23	22	22	21	20	20	19	19	19	18	18	18	19	19	19	20	20	20	19	19	18	18	17	17
Humid (%)	5	5	4	4	4	4	4	4	4	4	4	4	4	3	3	3	2	2	2	1	1	1	1	0	0	0	0	0	0	0

	Dry (%)	Comfortable (%)	Humid (%)
1	68	27	5
2	69	26	5
3	70	26	4
4	71	25	4
5	72	24	4
6	72	24	4
7	73	23	4
8	74	22	4
9	74	22	4
10	75	21	4
11	76	20	4
12	76	20	4
13	77	19	4
14	78	19	3
15	78	19	3
16	79	18	3
17	80	18	2
18	80	18	2
19	79	19	2
20	80	19	1
21	80	19	1
22	79	20	1
23	79	20	1
24	80	20	0
25	81	19	0
26	81	19	0
27	82	18	0
28	82	18	0
29	83	17	0
30	83	17	0

Wind in September

Winds average 14 km/h in September.

Across September, daily wind ranges from about 14 km/h on the calmest days to 15 km/h at its breeziest. It stays fairly steady from day to day.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Wind speed (km/h)	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	14	15	15	15	15	15	15
Feels	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze	light breeze

	Wind speed (km/h)	Feels
1	14	light breeze
2	14	light breeze
3	14	light breeze
4	14	light breeze
5	14	light breeze
6	14	light breeze
7	14	light breeze
8	14	light breeze
9	14	light breeze
10	14	light breeze
11	14	light breeze
12	14	light breeze
13	14	light breeze
14	14	light breeze
15	14	light breeze
16	14	light breeze
17	14	light breeze
18	14	light breeze
19	14	light breeze
20	14	light breeze
21	14	light breeze
22	14	light breeze
23	14	light breeze
24	14	light breeze
25	15	light breeze
26	15	light breeze
27	15	light breeze
28	15	light breeze
29	15	light breeze
30	15	light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 24 min at the start of September to 11 h 24 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 120 minutes over September. Sunrise moves from 5:18 AM to 6:07 AM, and sunset from 6:43 PM to 5:33 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Daylight (h)	13.4	13.3	13.3	13.2	13.1	13.1	13.0	12.9	12.9	12.8	12.7	12.7	12.6	12.5	12.5	12.4	12.3	12.3	12.2	12.1	12.1	12.0	11.9	11.8	11.8	11.7	11.6	11.6	11.5	11.4
Sunrise (AM)	5:18	5:20	5:22	5:23	5:25	5:27	5:28	5:30	5:32	5:33	5:35	5:37	5:38	5:40	5:42	5:43	5:45	5:47	5:48	5:50	5:52	5:53	5:55	5:57	5:59	6:00	6:02	6:04	6:05	6:07
Sunset (PM)	6:43	6:40	6:38	6:36	6:33	6:31	6:29	6:26	6:24	6:21	6:19	6:17	6:14	6:12	6:09	6:07	6:05	6:02	6:00	5:57	5:55	5:52	5:50	5:48	5:45	5:43	5:40	5:38	5:36	5:33

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	13.4	5:18	6:43
2	13.3	5:20	6:40
3	13.3	5:22	6:38
4	13.2	5:23	6:36
5	13.1	5:25	6:33
6	13.1	5:27	6:31
7	13.0	5:28	6:29
8	12.9	5:30	6:26
9	12.9	5:32	6:24
10	12.8	5:33	6:21
11	12.7	5:35	6:19
12	12.7	5:37	6:17
13	12.6	5:38	6:14
14	12.5	5:40	6:12
15	12.5	5:42	6:09
16	12.4	5:43	6:07
17	12.3	5:45	6:05
18	12.3	5:47	6:02
19	12.2	5:48	6:00
20	12.1	5:50	5:57
21	12.1	5:52	5:55
22	12.0	5:53	5:52
23	11.9	5:55	5:50
24	11.8	5:57	5:48
25	11.8	5:59	5:45
26	11.7	6:00	5:43
27	11.6	6:02	5:40
28	11.6	6:04	5:38
29	11.5	6:05	5:36
30	11.4	6:07	5:33

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.99 kWh/m².

For context, solar energy here swings from a low near 0.63 kWh/m² to a high of 5.16 kWh/m² in June across the year — September's 2.99 kWh/m² falls in the middle.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Solar energy (kWh/m²)	3.6	3.5	3.5	3.5	3.4	3.4	3.4	3.3	3.3	3.2	3.2	3.1	3.1	3.0	3.0	3.0	2.9	2.9	2.8	2.8	2.7	2.7	2.6	2.6	2.6	2.5	2.5	2.4	2.4	2.4
Level	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate

	Solar energy (kWh/m²)	Level
1	3.6	Moderate
2	3.5	Moderate
3	3.5	Moderate
4	3.5	Moderate
5	3.4	Moderate
6	3.4	Moderate
7	3.4	Moderate
8	3.3	Moderate
9	3.3	Moderate
10	3.2	Moderate
11	3.2	Moderate
12	3.1	Moderate
13	3.1	Moderate
14	3.0	Moderate
15	3.0	Moderate
16	3.0	Moderate
17	2.9	Moderate
18	2.9	Moderate
19	2.8	Moderate
20	2.8	Moderate
21	2.7	Moderate
22	2.7	Moderate
23	2.6	Moderate
24	2.6	Moderate
25	2.6	Moderate
26	2.5	Moderate
27	2.5	Moderate
28	2.4	Moderate
29	2.4	Moderate
30	2.4	Moderate

Planning a trip in September

Is September a good time to visit Welwyn Garden City?

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

5.7

Sightseeing

4th-best month of the year

2.0

Beach & pool

4th-best month of the year

September is a reasonable time to visit Welwyn Garden City for sightseeing.

What to pack for Welwyn Garden City in September

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

In September, Welwyn Garden City sees daytime highs around 18°C and nights near 11°C. Worth packing: rain gear. About 10 days see rain.

rain gear

UV index in Welwyn Garden City 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 Welwyn Garden City peaks around August 10 at about 6 (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 6 months of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	1	1	3	3	5	6	6	6	4	2	1	1
Level	Low	Low	Moderate	Moderate	High	High	High	High	Moderate	Moderate	Low	Low

	UV index (midday)	Level
Jan	1	Low
Feb	1	Low
Mar	3	Moderate
Apr	3	Moderate
May	5	High
Jun	6	High
Jul	6	High
Aug	6	High
Sep	4	Moderate
Oct	2	Moderate
Nov	1	Low
Dec	1	Low

Location & terrain

Where is Welwyn Garden City?

Welwyn Garden City sits at 51.8°N, 0.2°W, 92 m above sea level, in United Kingdom. The nearest listed city is Hatfield, 4.0 km away.

Topography around Welwyn Garden City

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

Within 3 km, the terrain around Welwyn Garden City has only modest variations in elevation — a maximum elevation change of 90 m around an average of 87 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 164 m; within 80 km, significant variations in elevation — a maximum elevation change of 307 m.

The land around Welwyn Garden City is covered by trees (44%) and grassland (22%) within 3 km, cropland (32%), trees (31%) and grassland (27%) within 16 km, and cropland (39%), grassland (27%) and trees (21%) within 80 km.

3 km

90 m

trees 44%

16 km

164 m

cropland 32%

80 km

307 m

cropland 39%

treesgrasslandcroplandartificial surfaceswater

← August Welwyn Garden City year-round climate October →Best places to visit in September

September weather nearby: Hatfield 4.0 km · Hertford 9.0 km · St Albans 10 km · Harpenden 10 km · Stevenage 11 km · Potters Bar 12 km · Ware 12 km · Hoddesdon 14 km

United Kingdom travel facts

Travel advisory: Level 2; Exercise Increased Caution
Power plugs: Type D / G / M; 230 V · 50 Hz
Prices: ≈ 89% of US; price level, 2025
GDP per capita: $57,602; 2025
Happiness: 6.7 / 10; World Happiness, 2025
Safe drinking water: 100%; of population, 2024
Homicide rate: 1.1; per 100k, 2021
Road deaths: 3.2; per 100k/yr, 2019
Income group: High; World Bank
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 Welwyn Garden City (51.8017°, -0.2069°, elevation 92 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. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).

	Avg high (°C)	Avg low (°C)
1	20	12
2	20	12
3	20	12
4	19	12
5	19	12
6	19	12
7	19	11
8	19	11
9	19	11
10	19	11
11	19	11
12	19	11
13	19	11
14	18	11
15	18	11
16	18	11
17	18	11
18	18	11
19	18	11
20	18	11
21	18	10
22	18	10
23	17	10
24	17	10
25	17	10
26	17	10
27	17	10
28	17	10
29	17	10
30	16	10

	Clearer (%)	Cloudier (%)
1	33	67
2	33	67
3	33	67
4	33	67
5	33	67
6	32	68
7	32	68
8	33	67
9	32	68
10	32	68
11	32	68
12	30	70
13	31	69
14	30	70
15	30	70
16	29	71
17	29	71
18	28	72
19	27	73
20	27	73
21	27	73
22	27	73
23	27	73
24	27	73
25	27	73
26	26	74
27	27	73
28	27	73
29	27	73
30	28	72

	Rain chance (%)
1	30
2	29
3	29
4	29
5	29
6	29
7	29
8	29
9	30
10	30
11	30
12	30
13	30
14	30
15	30
16	31
17	31
18	32
19	32
20	32
21	33
22	33
23	34
24	35
25	35
26	36
27	36
28	37
29	37
30	38

	Dry (%)	Comfortable (%)	Humid (%)
1	68	27	5
2	69	26	5
3	70	26	4
4	71	25	4
5	72	24	4
6	72	24	4
7	73	23	4
8	74	22	4
9	74	22	4
10	75	21	4
11	76	20	4
12	76	20	4
13	77	19	4
14	78	19	3
15	78	19	3
16	79	18	3
17	80	18	2
18	80	18	2
19	79	19	2
20	80	19	1
21	80	19	1
22	79	20	1
23	79	20	1
24	80	20	0
25	81	19	0
26	81	19	0
27	82	18	0
28	82	18	0
29	83	17	0
30	83	17	0

	Avg high (°C)	Avg low (°C)
1	20	12
2	20	12
3	20	12
4	19	12
5	19	12
6	19	12
7	19	11
8	19	11
9	19	11
10	19	11
11	19	11
12	19	11
13	19	11
14	18	11
15	18	11
16	18	11
17	18	11
18	18	11
19	18	11
20	18	11
21	18	10
22	18	10
23	17	10
24	17	10
25	17	10
26	17	10
27	17	10
28	17	10
29	17	10
30	16	10

	Clearer (%)	Cloudier (%)
1	33	67
2	33	67
3	33	67
4	33	67
5	33	67
6	32	68
7	32	68
8	33	67
9	32	68
10	32	68
11	32	68
12	30	70
13	31	69
14	30	70
15	30	70
16	29	71
17	29	71
18	28	72
19	27	73
20	27	73
21	27	73
22	27	73
23	27	73
24	27	73
25	27	73
26	26	74
27	27	73
28	27	73
29	27	73
30	28	72

	Rain chance (%)
1	30
2	29
3	29
4	29
5	29
6	29
7	29
8	29
9	30
10	30
11	30
12	30
13	30
14	30
15	30
16	31
17	31
18	32
19	32
20	32
21	33
22	33
23	34
24	35
25	35
26	36
27	36
28	37
29	37
30	38

	Dry (%)	Comfortable (%)	Humid (%)
1	68	27	5
2	69	26	5
3	70	26	4
4	71	25	4
5	72	24	4
6	72	24	4
7	73	23	4
8	74	22	4
9	74	22	4
10	75	21	4
11	76	20	4
12	76	20	4
13	77	19	4
14	78	19	3
15	78	19	3
16	79	18	3
17	80	18	2
18	80	18	2
19	79	19	2
20	80	19	1
21	80	19	1
22	79	20	1
23	79	20	1
24	80	20	0
25	81	19	0
26	81	19	0
27	82	18	0
28	82	18	0
29	83	17	0
30	83	17	0

	Avg high (°C)	Avg low (°C)
1	20	12
2	20	12
3	20	12
4	19	12
5	19	12
6	19	12
7	19	11
8	19	11
9	19	11
10	19	11
11	19	11
12	19	11
13	19	11
14	18	11
15	18	11
16	18	11
17	18	11
18	18	11
19	18	11
20	18	11
21	18	10
22	18	10
23	17	10
24	17	10
25	17	10
26	17	10
27	17	10
28	17	10
29	17	10
30	16	10

	Clearer (%)	Cloudier (%)
1	33	67
2	33	67
3	33	67
4	33	67
5	33	67
6	32	68
7	32	68
8	33	67
9	32	68
10	32	68
11	32	68
12	30	70
13	31	69
14	30	70
15	30	70
16	29	71
17	29	71
18	28	72
19	27	73
20	27	73
21	27	73
22	27	73
23	27	73
24	27	73
25	27	73
26	26	74
27	27	73
28	27	73
29	27	73
30	28	72

	Rain chance (%)
1	30
2	29
3	29
4	29
5	29
6	29
7	29
8	29
9	30
10	30
11	30
12	30
13	30
14	30
15	30
16	31
17	31
18	32
19	32
20	32
21	33
22	33
23	34
24	35
25	35
26	36
27	36
28	37
29	37
30	38

	Dry (%)	Comfortable (%)	Humid (%)
1	68	27	5
2	69	26	5
3	70	26	4
4	71	25	4
5	72	24	4
6	72	24	4
7	73	23	4
8	74	22	4
9	74	22	4
10	75	21	4
11	76	20	4
12	76	20	4
13	77	19	4
14	78	19	3
15	78	19	3
16	79	18	3
17	80	18	2
18	80	18	2
19	79	19	2
20	80	19	1
21	80	19	1
22	79	20	1
23	79	20	1
24	80	20	0
25	81	19	0
26	81	19	0
27	82	18	0
28	82	18	0
29	83	17	0
30	83	17	0