Ostrołęka weather in September

In September, Ostrołęka sees average daytime highs of 18°C and overnight lows near 9°C, with 57 mm of rain across 9.7 wet days and about 12.4 hours of daylight. It is the 5th-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 20°C in the first days to 16°C by the end. The sky is clear or mostly clear about 22% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 30 min at the start of September to 11 h 24 min by month's end. Set against the rest of the year, September is Ostrołęka's 6th-clearest and 8th-windiest month. For the whole year in context, see Ostrołęka's year-round climate.

Daytime high: 18°; 5th warmest
Overnight low: 9°; 9th coldest
Rainfall: 57 mm; 9.7 wet days
Daylight: 12 h 24 min; 5:16 AM – 5:40 PM
Cloud cover: 65%; 6th clearest
Wind: 12 km/h; 8th windiest
Solar energy: 2.92 kWh/m²
Travel score: 5.7; out of 10

Ostrołęka is city with powiat rights of Poland.

Density: 1,919/km²; people per km²
Founded: 1050

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

← August Ostrołęka 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 20°C in the first days to 16°C by the end.

A typical September day in Ostrołęka reaches about 18°C in the afternoon and slips back to 9°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 13°C and 23°C. Set against its neighbours, September runs about 5°C cooler than August and about 6°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)	21	21	20	20	20	20	20	19	19	19	19	19	19	18	18	18	18	18	17	17	17	17	17	17	16	16	16	16	16	15
Avg low (°C)	11	11	11	11	11	10	10	10	10	10	10	10	9	9	9	9	9	9	8	8	8	8	8	8	8	8	7	7	7	7

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

How September really feels in Ostrołęka

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.

Ostrołęka weather by month

How September compares with the rest of the year at a glance. September is the 5th-warmest and 5th-wettest month here — the current month is highlighted below.

Month	High / Low (°C)	Rainfall (mm)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	0° / -4°	39	10.3	6.3	7.9	0.0
Feb	2° / -4°	36	9.1	5.5	9.5	0.0
Mar	6° / -1°	39	10	3.2	11.5	0.6
Apr	13° / 3°	44	10.1	0.9	13.6	3.6
May	19° / 8°	66	11.9	0	15.5	5.7
Jun	22° / 11°	70	11.8	0	16.6	6.2
Jul	24° / 14°	79	12.2	0	16.2	6.6
Aug	23° / 13°	62	10.6	0	14.5	6.7
Sep	18° / 9°	57	9.7	0	12.4	5.7
Oct	12° / 5°	47	9.6	0.3	10.3	3.1
Nov	6° / 1°	39	9.6	2.5	8.4	0.4
Dec	2° / -3°	42	9.7	4.7	7.4	0.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 22% 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 62%.

	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 (%)	42	42	41	41	40	39	40	39	39	38	37	36	37	37	37	37	37	37	37	37	37	37	38	38	37	36	36	36	36	37
Cloudier (%)	58	58	59	59	60	61	60	61	61	62	63	64	63	63	63	63	63	63	63	63	63	63	62	62	63	64	64	64	64	63

	Clearer (%)	Cloudier (%)
1	42	58
2	42	58
3	41	59
4	41	59
5	40	60
6	39	61
7	40	60
8	39	61
9	39	61
10	38	62
11	37	63
12	36	64
13	37	63
14	37	63
15	37	63
16	37	63
17	37	63
18	37	63
19	37	63
20	37	63
21	37	63
22	37	63
23	38	62
24	38	62
25	37	63
26	36	64
27	36	64
28	36	64
29	36	64
30	37	63

Chance of precipitation in September

Any precipitation

Ostrołęka gets around 57 mm of rain over 9.7 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 37% on the wettest days. The odds ease 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 (%)	37	37	37	36	36	36	36	35	35	34	34	33	32	32	31	31	30	30	29	29	29	29	29	29	29	29	30	30	30	31

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

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 84% 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 (%)	71	71	73	73	74	75	76	76	77	79	80	81	82	83	84	85	86	87	89	90	91	92	92	94	94	94	94	94	95	95
Comfortable (%)	25	25	24	24	23	22	21	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	7	6	6	6	6	6	5	5
Humid (%)	4	4	3	3	3	3	3	3	3	2	2	2	2	2	2	2	2	2	1	1	1	1	1	0	0	0	0	0	0	0

	Dry (%)	Comfortable (%)	Humid (%)
1	71	25	4
2	71	25	4
3	73	24	3
4	73	24	3
5	74	23	3
6	75	22	3
7	76	21	3
8	76	21	3
9	77	20	3
10	79	19	2
11	80	18	2
12	81	17	2
13	82	16	2
14	83	15	2
15	84	14	2
16	85	13	2
17	86	12	2
18	87	11	2
19	89	10	1
20	90	9	1
21	91	8	1
22	92	7	1
23	92	7	1
24	94	6	0
25	94	6	0
26	94	6	0
27	94	6	0
28	94	6	0
29	95	5	0
30	95	5	0

Wind in September

Winds average 12 km/h in September.

Across September, daily wind ranges from about 12 km/h on the calmest days to 13 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)	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	13	13	13	13	13	13	13	13	13	13
Feels	calm	calm	calm	calm	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	12	calm
2	12	calm
3	12	calm
4	12	calm
5	12	light breeze
6	12	light breeze
7	12	light breeze
8	12	light breeze
9	12	light breeze
10	12	light breeze
11	12	light breeze
12	12	light breeze
13	12	light breeze
14	12	light breeze
15	12	light breeze
16	12	light breeze
17	12	light breeze
18	12	light breeze
19	12	light breeze
20	12	light breeze
21	13	light breeze
22	13	light breeze
23	13	light breeze
24	13	light breeze
25	13	light breeze
26	13	light breeze
27	13	light breeze
28	13	light breeze
29	13	light breeze
30	13	light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 30 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 126 minutes over September. Sunrise moves from 4:49 AM to 5:41 AM, and sunset from 6:18 PM to 5:05 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)	13.5	13.4	13.3	13.3	13.2	13.1	13.1	13.0	12.9	12.8	12.8	12.7	12.6	12.6	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)	4:49	4:51	4:53	4:54	4:56	4:58	5:00	5:02	5:03	5:05	5:07	5:09	5:10	5:12	5:14	5:16	5:17	5:19	5:21	5:23	5:25	5:26	5:28	5:30	5:32	5:33	5:35	5:37	5:39	5:41
Sunset (PM)	6:18	6:15	6:13	6:10	6:08	6:05	6:03	6:00	5:58	5:55	5:53	5:50	5:48	5:45	5:43	5:40	5:38	5:35	5:33	5:30	5:28	5:25	5:23	5:20	5:18	5:15	5:13	5:10	5:08	5:05

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	13.5	4:49	6:18
2	13.4	4:51	6:15
3	13.3	4:53	6:13
4	13.3	4:54	6:10
5	13.2	4:56	6:08
6	13.1	4:58	6:05
7	13.1	5:00	6:03
8	13.0	5:02	6:00
9	12.9	5:03	5:58
10	12.8	5:05	5:55
11	12.8	5:07	5:53
12	12.7	5:09	5:50
13	12.6	5:10	5:48
14	12.6	5:12	5:45
15	12.5	5:14	5:43
16	12.4	5:16	5:40
17	12.3	5:17	5:38
18	12.3	5:19	5:35
19	12.2	5:21	5:33
20	12.1	5:23	5:30
21	12.1	5:25	5:28
22	12.0	5:26	5:25
23	11.9	5:28	5:23
24	11.8	5:30	5:20
25	11.8	5:32	5:18
26	11.7	5:33	5:15
27	11.6	5:35	5:13
28	11.6	5:37	5:10
29	11.5	5:39	5:08
30	11.4	5:41	5:05

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.92 kWh/m².

For context, solar energy here swings from a low near 0.48 kWh/m² to a high of 5.46 kWh/m² in June across the year — September's 2.92 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	3.3	3.3	3.2	3.2	3.1	3.1	3.0	3.0	3.0	2.9	2.9	2.8	2.8	2.8	2.7	2.7	2.6	2.6	2.5	2.5	2.5	2.4	2.4	2.3
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	3.3	Moderate
8	3.3	Moderate
9	3.2	Moderate
10	3.2	Moderate
11	3.1	Moderate
12	3.1	Moderate
13	3.0	Moderate
14	3.0	Moderate
15	3.0	Moderate
16	2.9	Moderate
17	2.9	Moderate
18	2.8	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	2.5	Moderate
26	2.5	Moderate
27	2.5	Moderate
28	2.4	Moderate
29	2.4	Moderate
30	2.3	Moderate

Planning a trip in September

Is September a good time to visit Ostrołęka?

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

5th-best month of the year

September is a reasonable time to visit Ostrołęka for sightseeing.

What to pack for Ostrołęka in September

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

In September, Ostrołęka sees daytime highs around 18°C and nights near 9°C. Worth packing: rain gear. About 10 days see rain.

rain gear

UV index in Ostrołęka 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 Ostrołęka peaks around June 20 at about 6 (high) — a little sun protection helps at midday. It bottoms out near December 19 at about 0 (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	4	5	6	6	6	4	2	1	0
Level	Low	Low	Moderate	Moderate	High	High	High	High	Moderate	Low	Low	Low

	UV index (midday)	Level
Jan	1	Low
Feb	1	Low
Mar	3	Moderate
Apr	4	Moderate
May	5	High
Jun	6	High
Jul	6	High
Aug	6	High
Sep	4	Moderate
Oct	2	Low
Nov	1	Low
Dec	0	Low

Location & terrain

Where is Ostrołęka?

Ostrołęka sits at 53.1°N, 21.6°E, 97 m above sea level, in Poland. The nearest listed city is Łomża, 34 km away.

Topography around Ostrołęka

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

Within 3 km, the terrain around Ostrołęka has only modest variations in elevation — a maximum elevation change of 32 m around an average of 100 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 58 m; within 80 km, only modest variations in elevation — a maximum elevation change of 168 m.

The land around Ostrołęka is covered by trees (39%), grassland (30%) and artificial surfaces (26%) within 3 km, trees (42%) and grassland (36%) within 16 km, and trees (39%), cropland (30%) and grassland (28%) within 80 km.

3 km

32 m

trees 39%

16 km

58 m

trees 42%

80 km

168 m

trees 39%

treesgrasslandcroplandartificial surfaceswaterwetland

← August Ostrołęka year-round climate October →Best places to visit in September

September weather nearby: Łomża 34 km · Ostrów Mazowiecka 38 km · Zambrów 46 km · Przasnysz 47 km · Pułtusk 54 km · Wyszków 55 km · Pisz 62 km · Szczytno 66 km

Poland travel facts

Travel advisory: Level 1; Exercise Normal Precautions
Power plugs: Type C / E; 230 V · 50 Hz
Prices: ≈ 52% of US; price level, 2025
GDP per capita: $28,420; 2025
Happiness: 6.8 / 10; World Happiness, 2025
Safe drinking water: 89%; of population, 2024
Homicide rate: 0.8; per 100k, 2023
Road deaths: 9.4; per 100k/yr, 2019
Income group: High; World Bank
English: Very high; EF EPI 600
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 Ostrołęka (53.0862°, 21.5757°, elevation 97 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	21	11
2	21	11
3	20	11
4	20	11
5	20	11
6	20	10
7	20	10
8	19	10
9	19	10
10	19	10
11	19	10
12	19	10
13	19	9
14	18	9
15	18	9
16	18	9
17	18	9
18	18	9
19	17	8
20	17	8
21	17	8
22	17	8
23	17	8
24	17	8
25	16	8
26	16	8
27	16	7
28	16	7
29	16	7
30	15	7

	Clearer (%)	Cloudier (%)
1	42	58
2	42	58
3	41	59
4	41	59
5	40	60
6	39	61
7	40	60
8	39	61
9	39	61
10	38	62
11	37	63
12	36	64
13	37	63
14	37	63
15	37	63
16	37	63
17	37	63
18	37	63
19	37	63
20	37	63
21	37	63
22	37	63
23	38	62
24	38	62
25	37	63
26	36	64
27	36	64
28	36	64
29	36	64
30	37	63

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

	Dry (%)	Comfortable (%)	Humid (%)
1	71	25	4
2	71	25	4
3	73	24	3
4	73	24	3
5	74	23	3
6	75	22	3
7	76	21	3
8	76	21	3
9	77	20	3
10	79	19	2
11	80	18	2
12	81	17	2
13	82	16	2
14	83	15	2
15	84	14	2
16	85	13	2
17	86	12	2
18	87	11	2
19	89	10	1
20	90	9	1
21	91	8	1
22	92	7	1
23	92	7	1
24	94	6	0
25	94	6	0
26	94	6	0
27	94	6	0
28	94	6	0
29	95	5	0
30	95	5	0

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

	Clearer (%)	Cloudier (%)
1	42	58
2	42	58
3	41	59
4	41	59
5	40	60
6	39	61
7	40	60
8	39	61
9	39	61
10	38	62
11	37	63
12	36	64
13	37	63
14	37	63
15	37	63
16	37	63
17	37	63
18	37	63
19	37	63
20	37	63
21	37	63
22	37	63
23	38	62
24	38	62
25	37	63
26	36	64
27	36	64
28	36	64
29	36	64
30	37	63

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

	Dry (%)	Comfortable (%)	Humid (%)
1	71	25	4
2	71	25	4
3	73	24	3
4	73	24	3
5	74	23	3
6	75	22	3
7	76	21	3
8	76	21	3
9	77	20	3
10	79	19	2
11	80	18	2
12	81	17	2
13	82	16	2
14	83	15	2
15	84	14	2
16	85	13	2
17	86	12	2
18	87	11	2
19	89	10	1
20	90	9	1
21	91	8	1
22	92	7	1
23	92	7	1
24	94	6	0
25	94	6	0
26	94	6	0
27	94	6	0
28	94	6	0
29	95	5	0
30	95	5	0

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

	Clearer (%)	Cloudier (%)
1	42	58
2	42	58
3	41	59
4	41	59
5	40	60
6	39	61
7	40	60
8	39	61
9	39	61
10	38	62
11	37	63
12	36	64
13	37	63
14	37	63
15	37	63
16	37	63
17	37	63
18	37	63
19	37	63
20	37	63
21	37	63
22	37	63
23	38	62
24	38	62
25	37	63
26	36	64
27	36	64
28	36	64
29	36	64
30	37	63

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

	Dry (%)	Comfortable (%)	Humid (%)
1	71	25	4
2	71	25	4
3	73	24	3
4	73	24	3
5	74	23	3
6	75	22	3
7	76	21	3
8	76	21	3
9	77	20	3
10	79	19	2
11	80	18	2
12	81	17	2
13	82	16	2
14	83	15	2
15	84	14	2
16	85	13	2
17	86	12	2
18	87	11	2
19	89	10	1
20	90	9	1
21	91	8	1
22	92	7	1
23	92	7	1
24	94	6	0
25	94	6	0
26	94	6	0
27	94	6	0
28	94	6	0
29	95	5	0
30	95	5	0