Bolu weather in September

In September, Bolu sees average daytime highs of 22°C and overnight lows near 11°C, with 66 mm of rain across 8.8 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 10th-wettest month of the year here.

Highs ease over the month, from about 23°C in the first days to 20°C by the end. The sky is clear or mostly clear about 51% 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 Bolu's 3rd-clearest and 11th-windiest month. For the whole year in context, see Bolu's year-round climate.

Daytime high
22°
3rd warmest
Overnight low
11°
9th coldest
Rainfall
66 mm
8.8 wet days
Daylight
12 h 18 min
5:40 AM – 5:56 PM
Cloud cover
41%
3rd clearest
Wind
5 km/h
11th windiest
Solar energy
4.77 kWh/m²
Travel score
7.1
out of 10

Bolu is central district and city in Bolu Province, Turkey.

Air quality
Elevated
PM2.5 24.4 µg/m³ · 2019
Density
6,840/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 23°C in the first days to 20°C by the end.

A typical September day in Bolu reaches about 22°C in the afternoon and slips back to 11°C overnight — a 11°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 3°C cooler than August and about 5°C warmer than October.

10°20°30°151015202530
Avg high (°C)Avg low (°C)
12412
22312
32312
42312
52312
62312
72312
82311
92311
102211
112211
122211
132211
142211
152211
162211
172211
182110
192110
202110
212110
222110
232110
242110
252110
26209
27209
28209
29209
30209

How September really feels in Bolu

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.

Bolu weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -4°9113.9119.40.0
Feb / -3°8813.81010.40.2
Mar / -0°10714.98.511.71.6
Apr14° / 9914.42.513.13.5
May18° / 11015.90.114.25.2
Jun22° / 11°9613.3014.96.3
Jul24° / 14°508.6014.67.6
Aug25° / 14°528.3013.67.7
Sep22° / 11°668.8012.37.1
Oct17° / 9011.20.810.95.4
Nov11° / 7510.33.69.72.8
Dec / -2°9613.48.29.10.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 51% 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 31%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17525
27525
37525
47426
57426
67426
77426
87327
97228
107228
117228
127228
137129
147129
157030
166832
176832
186733
196634
206634
216535
226436
236436
246337
256337
266238
276238
286337
296337
306238

Chance of precipitation in September

Any precipitation

Bolu gets around 66 mm of rain over 8.8 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 29% and peaks near 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
130
230
330
430
529
629
729
828
927
1027
1127
1226
1326
1426
1527
1627
1727
1828
1928
2029
2129
2230
2330
2431
2531
2631
2731
2831
2931
3030

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 69% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
14837141
25036131
35235121
45434111
55733100
6583390
7603280
8623170
9623170
10633160
11653050
12653050
13663040
14663040
15682930
16682930
17692830
18712720
19722620
20732520
21762310
22772210
23792010
24811810
25831610
26851500
27871300
28881200
29891100
3091900

Wind in September

Winds average 5 km/h in September.

Across September, daily wind ranges from about 5 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm

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 5:25 AM to 5:54 AM, and sunset from 6:22 PM to 5:31 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:256:22
212.95:266:20
312.95:276:18
412.85:286:17
512.85:296:15
612.75:306:13
712.75:316:12
812.65:326:10
912.65:336:08
1012.55:346:06
1112.55:356:05
1212.55:366:03
1312.45:376:01
1412.45:385:59
1512.35:395:58
1612.35:405:56
1712.25:415:54
1812.25:425:52
1912.15:435:51
2012.15:445:49
2112.05:455:47
2212.05:465:45
2311.95:475:44
2411.95:485:42
2511.85:495:40
2611.85:505:38
2711.85:515:37
2811.75:525:35
2911.75:535:33
3011.65:545:31

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.77 kWh/m².

For context, solar energy here swings from a low near 1.72 kWh/m² to a high of 6.88 kWh/m² in July across the year — September's 4.77 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.5Bright
25.4Bright
35.4Bright
45.3Bright
55.3Bright
65.3Bright
75.2Bright
85.2Bright
95.1Bright
105.1Bright
115.0Bright
125.0Bright
134.9Bright
144.9Bright
154.8Bright
164.8Bright
174.7Bright
184.7Bright
194.6Bright
204.5Bright
214.5Bright
224.4Bright
234.4Bright
244.3Bright
254.3Bright
264.3Bright
274.2Bright
284.2Bright
294.1Bright
304.1Bright
Planning a trip in September

Is September a good time to visit Bolu?

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

7.1
Sightseeing
3rd-best month of the year
4.8
Beach & pool
3rd-best month of the year

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

What to pack for Bolu in September

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

In September, Bolu sees daytime highs around 22°C and nights near 11°C. Worth packing: rain gear and sun protection. About 9 days see rain.

rain gearsun protection

Sea temperature near Bolu in September

The nearest coast averages about 23°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 47 km away) is warmest in August at about 25°C and coldest in February near 7°C.

It's comfortable for a long swim from Jun 11 to Oct 12 — about 4.1 months when the water holds above 20°C.

10°20°30°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan9Bracing
Feb7Bracing
Mar8Bracing
Apr11Bracing
May16Cool
Jun21Refreshing
Jul24Refreshing
Aug25Warm
Sep23Refreshing
Oct20Cool
Nov15Cool
Dec12Bracing

UV index in Bolu 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 Bolu peaks around August 10 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowAug 10UV 9Dec 19UV 2
UV index (midday)Level
Jan2Low
Feb2Moderate
Mar3Moderate
Apr7High
May7Very high
Jun9Very high
Jul9Very high
Aug9Very high
Sep6High
Oct4Moderate
Nov2Moderate
Dec2Low

Air quality in Bolu 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 Bolu is worst in May — around 33 µg/m³ PM2.5 (moderate), about 1.7× the cleanest month (December, 19 µg/m³).

Seasonal pattern from CAMS reanalysis, scaled to Bolu's WHO annual average of 24.4 µg/m³.

010203040JanFebMarAprMayJunJulAugSepOctNovDecModerateMay 933 µg/m³Dec 2319 µg/m³
PM2.5 (µg/m³)Level
Jan20Moderate
Feb23Moderate
Mar32Moderate
Apr33Moderate
May33Moderate
Jun26Moderate
Jul21Moderate
Aug21Moderate
Sep20Moderate
Oct22Moderate
Nov22Moderate
Dec19Moderate
Location & terrain

Where is Bolu?

Bolu sits at 40.7°N, 31.6°E, 733 m above sea level, in Turkey. The nearest listed city is Kaynaşlı, 24 km away.

Topography around Bolu

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

Within 3 km, the terrain around Bolu has only modest variations in elevation — a maximum elevation change of 178 m around an average of 745 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,296 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,359 m.

The land around Bolu is covered by artificial surfaces (51%) and cropland (33%) within 3 km, trees (67%) within 16 km, and trees (63%) and grassland (21%) within 80 km.

3 km
178 m
16 km
1,296 m
80 km
2,359 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Kaynaşlı 24 km · Düzce 39 km · Gerede 50 km · Alaplı 53 km · Akçakoca 56 km · Devrek 61 km · Ereğli 63 km · Nallıhan 65 km

Turkey travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 41% of US
price level, 2025
GDP per capita
$18,599
2025
Happiness
5.3 / 10
World Happiness, 2025
Homicide rate
3.2
per 100k, 2023
Road deaths
6.7
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Low
EF EPI 488
Religion
Muslim 100%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 Bolu (40.7358°, 31.6061°, elevation 733 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. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).