Sliven weather in September

In September, Sliven sees average daytime highs of 22°C and overnight lows near 12°C, with 58 mm of rain across 7.8 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 25°C in the first days to 20°C by the end. The sky is clear or mostly clear about 47% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Sliven's 3rd-clearest and 6th-windiest month. For the whole year in context, see Sliven's year-round climate.

Daytime high
22°
4th warmest
Overnight low
12°
9th coldest
Rainfall
58 mm
7.8 wet days
Daylight
12 h 18 min
6:00 AM – 6:18 PM
Cloud cover
46%
3rd clearest
Wind
8 km/h
6th windiest
Solar energy
4.37 kWh/m²
Travel score
7.3
out of 10

Sliven is city in Sliven municipality, Sliven oblast, Bulgaria.

Air quality
Good
PM10 17.8 µg/m³ · 2019
Density
432/km²
people per km²

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 25°C in the first days to 20°C by the end.

A typical September day in Sliven reaches about 22°C in the afternoon and slips back to 12°C overnight — a 10°C spread between the day's warmth and the night's chill. On most days the high lands between 17°C and 27°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)
12514
22514
32514
42414
52414
62414
72413
82413
92413
102313
112313
122313
132313
142313
152312
162212
172212
182212
192212
202212
212112
222112
232111
242111
252111
262111
272011
282011
292011
302011

How September really feels in Sliven

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.

Sliven weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -3°537.75.19.20.0
Feb / -2°5485.110.30.3
Mar10° / 6710.74.311.62.0
Apr15° / 7512.30.913.14.2
May20° / 10°10614.5014.45.7
Jun24° / 14°10014015.16.3
Jul27° / 16°8911.7014.86.7
Aug27° / 16°568013.77.2
Sep22° / 12°587.8012.37.3
Oct16° / 637.80.410.85.4
Nov10° / 587.42.19.62.3
Dec / -1°638.64.58.90.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 47% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 35%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17525
27525
37327
47327
57228
67129
77030
87030
97030
107030
116931
126931
136832
146832
156733
166733
176634
186436
196436
206337
216238
226139
236040
245941
255842
265743
275644
285644
295446
305446

Chance of precipitation in September

Any precipitation

Sliven gets around 58 mm of rain over 7.8 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 25% and peaks near 27% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
127
227
326
426
526
625
725
824
924
1024
1123
1223
1323
1423
1523
1623
1723
1824
1924
2025
2125
2226
2326
2426
2527
2627
2727
2827
2927
3027

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 62% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
14339171
24638161
34837140
45136130
55236120
65535100
7563590
8563590
9583480
10593470
11593470
12613360
13613360
14613360
15623260
16633160
17633160
18643060
19652960
20652960
21662860
22682750
23682750
24692650
25702550
26712540
27722440
28742330
29742330
30752230

Wind in September

Winds average 8 km/h in September.

Across September, daily wind ranges from about 8 km/h on the calmest days to 8 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
58calm
68calm
78calm
88calm
98calm
108calm
118calm
128calm
138calm
148calm
158calm
168calm
178calm
188calm
198calm
208calm
218calm
228calm
238calm
248calm
258calm
268calm
278calm
288calm
298calm
308calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:44 AM to 6:16 AM, and sunset from 6:45 PM to 5:52 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:446:45
213.05:456:43
312.95:466:41
412.95:476:40
512.85:486:38
612.85:496:36
712.75:516:34
812.75:526:32
912.65:536:31
1012.65:546:29
1112.55:556:27
1212.55:566:25
1312.45:576:23
1412.45:586:21
1512.35:596:19
1612.36:006:18
1712.26:026:16
1812.26:036:14
1912.16:046:12
2012.16:056:10
2112.06:066:08
2212.06:076:06
2311.96:086:05
2411.96:096:03
2511.86:116:01
2611.86:125:59
2711.76:135:57
2811.76:145:55
2911.66:155:54
3011.66:165:52

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.37 kWh/m².

For context, solar energy here swings from a low near 1.43 kWh/m² to a high of 6.45 kWh/m² in June across the year — September's 4.37 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.1Bright
35.1Bright
45.0Bright
55.0Bright
64.9Bright
74.8Bright
84.8Bright
94.7Bright
104.7Bright
114.6Bright
124.6Bright
134.5Bright
144.5Bright
154.4Bright
164.4Bright
174.3Bright
184.2Bright
194.2Bright
204.1Bright
214.1Bright
224.0Bright
234.0Moderate
243.9Moderate
253.8Moderate
263.8Moderate
273.7Moderate
283.7Moderate
293.6Moderate
303.6Moderate
Planning a trip in September

Is September a good time to visit Sliven?

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

7.3
Sightseeing
1st-best month of the year
5.3
Beach & pool
4th-best month of the year

September is one of the better times to visit Sliven for general sightseeing.

What to pack for Sliven in September

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

In September, Sliven sees daytime highs around 22°C and nights near 12°C. Worth packing: light clothes. About 8 days see rain.

light clothes

UV index in Sliven in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Sliven peaks around July 17 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 17UV 9Dec 21UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar3Moderate
Apr8Very high
May6High
Jun8Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov2Low
Dec1Low

Air quality in Sliven 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 Sliven is worst in March — around 16 µg/m³ PM2.5 (moderate), about 1.6× the cleanest month (September, 10 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodMar 1916 µg/m³Sep 1910 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb14Moderate
Mar16Moderate
Apr15Moderate
May13Moderate
Jun13Moderate
Jul12Good
Aug11Good
Sep10Good
Oct10Good
Nov11Good
Dec11Good
Location & terrain

Where is Sliven?

Sliven sits at 42.7°N, 26.3°E, 281 m above sea level, in Bulgaria. The nearest listed city is Yambol, 27 km away.

Nova ZagoraKarnobatStara ZagoraTargovishteGorna OryahovitsaVeliko TarnovoPopovo

Topography around Sliven

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

Within 3 km, the terrain around Sliven has significant variations in elevation — a maximum elevation change of 598 m around an average of 351 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 1,041 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,510 m.

The land around Sliven is covered by trees (43%), artificial surfaces (33%) and grassland (21%) within 3 km, trees (52%) and cropland (29%) within 16 km, and trees (42%) and cropland (40%) within 80 km.

3 km
598 m
16 km
1,041 m
80 km
1,510 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Yambol 27 km · Nova Zagora 34 km · Karnobat 54 km · Stara Zagora 63 km · Targovishte 66 km · Gorna Oryahovitsa 71 km · Veliko Tarnovo 72 km · Popovo 74 km

Bulgaria travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 23% of US
price level, 2025
GDP per capita
$20,328
2025
Happiness
5.7 / 10
World Happiness, 2025
Safe drinking water
96%
of population, 2024
Homicide rate
1.1
per 100k, 2023
Road deaths
9.2
per 100k/yr, 2019
Income group
High
World Bank
English
High
EF EPI 594
Religion
Christian 65%Muslim 10%none 5%other 0%

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 Sliven (42.6861°, 26.3256°, elevation 281 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).