Lahti weather in September

In September, Lahti sees average daytime highs of 14°C and overnight lows near 7°C, with 51 mm of rain across 9.8 wet days and about 12.6 hours of daylight. It is the 5th-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 17°C in the first days to 12°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 14 hours at the start of September to 11 h 12 min by month's end. Set against the rest of the year, September is Lahti's 7th-clearest and 7th-windiest month. For the whole year in context, see Lahti's year-round climate.

Daytime high: 14°; 5th warmest
Overnight low: 7°; 9th coldest
Rainfall: 51 mm; 9.8 wet days
Daylight: 12 h 36 min; 5:55 AM – 6:28 PM
Cloud cover: 72%; 7th clearest
Wind: 12 km/h; 7th windiest
Solar energy: 2.21 kWh/m²
Travel score: 4.0; out of 10

Air quality: Excellent; PM2.5 4.3 µg/m³ · 2019

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

← August Lahti 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 17°C in the first days to 12°C by the end.

A typical September day in Lahti reaches about 14°C in the afternoon and slips back to 7°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 10°C and 18°C. Set against its neighbours, September runs about 5°C cooler than August and about 7°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)	17	17	17	17	16	16	16	16	16	15	15	15	15	15	14	14	14	14	14	13	13	13	13	13	12	12	12	12	11	11
Avg low (°C)	10	10	9	9	9	9	9	9	9	8	8	8	8	8	7	7	7	7	7	7	6	6	6	6	6	6	6	6	5	5

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

How September really feels in Lahti

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.

Lahti 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	-3° / -8°	41	10.3	10.7	6.1	0.0
Feb	-3° / -9°	34	8.2	8.7	8.5	0.0
Mar	1° / -6°	33	8.4	8.2	11.3	0.0
Apr	8° / -1°	35	8.8	3.4	14.2	1.3
May	15° / 5°	48	10	0.2	17	4.3
Jun	19° / 10°	75	12.3	0	18.7	5.5
Jul	21° / 13°	76	12.4	0	18	6.1
Aug	20° / 12°	68	11.7	0	15.5	5.8
Sep	14° / 7°	51	9.8	0	12.6	4.0
Oct	7° / 3°	56	11.1	1.6	9.7	1.0
Nov	2° / -1°	50	10.8	5.5	6.9	0.0
Dec	-1° / -5°	48	11.6	9.9	5.3	0.0

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 15% of September, with mostly cloudy or overcast conditions the remaining 71%.

	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 (%)	27	27	27	27	27	29	29	29	29	29	31	31	31	31	31	31	31	31	31	31	31	30	29	29	29	28	28	27	26	26
Cloudier (%)	73	73	73	73	73	71	71	71	71	71	69	69	69	69	69	69	69	69	69	69	69	70	71	71	71	72	72	73	74	74

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

Chance of precipitation in September

Any precipitation

Lahti gets around 51 mm of rain over 9.8 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 33% and peaks near 34% on the wettest days.

	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 (%)	34	34	34	34	34	34	34	34	34	34	34	34	34	34	34	34	33	33	33	32	32	31	31	31	31	31	31	31	31	32

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

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 93% 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 (%)	80	82	83	84	85	88	89	90	90	91	92	93	93	94	95	95	96	96	97	97	98	98	98	99	99	99	99	99	99	99
Comfortable (%)	19	17	16	15	14	12	11	10	10	9	8	7	7	6	5	5	4	4	3	3	2	2	2	1	1	1	1	1	1	1
Humid (%)	1	1	1	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

	Dry (%)	Comfortable (%)	Humid (%)
1	80	19	1
2	82	17	1
3	83	16	1
4	84	15	1
5	85	14	1
6	88	12	0
7	89	11	0
8	90	10	0
9	90	10	0
10	91	9	0
11	92	8	0
12	93	7	0
13	93	7	0
14	94	6	0
15	95	5	0
16	95	5	0
17	96	4	0
18	96	4	0
19	97	3	0
20	97	3	0
21	98	2	0
22	98	2	0
23	98	2	0
24	99	1	0
25	99	1	0
26	99	1	0
27	99	1	0
28	99	1	0
29	99	1	0
30	99	1	0

Wind in September

Winds average 12 km/h in September.

Across September, daily wind ranges from about 11 km/h on the calmest days to 12 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)	11	11	11	11	11	11	11	11	11	11	11	11	11	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12	12
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	light breeze

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

Sunrise & sunset in September

DaylightNight

Daylight runs from about 14 hours at the start of September to 11 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 168 minutes over September. Sunrise moves from 5:17 AM to 6:31 AM, and sunset from 7:17 PM to 5:43 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)	14.0	13.9	13.8	13.7	13.6	13.5	13.4	13.3	13.2	13.1	13.0	12.9	12.8	12.8	12.7	12.6	12.5	12.4	12.3	12.2	12.1	12.0	11.9	11.8	11.7	11.6	11.5	11.4	11.3	11.2
Sunrise (AM)	5:17	5:19	5:22	5:25	5:27	5:30	5:32	5:35	5:37	5:40	5:42	5:45	5:47	5:50	5:52	5:55	5:57	6:00	6:03	6:05	6:08	6:10	6:13	6:15	6:18	6:20	6:23	6:26	6:28	6:31
Sunset (PM)	7:17	7:14	7:11	7:08	7:04	7:01	6:58	6:55	6:51	6:48	6:45	6:42	6:38	6:35	6:32	6:28	6:25	6:22	6:19	6:15	6:12	6:09	6:05	6:02	5:59	5:56	5:52	5:49	5:46	5:43

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	14.0	5:17	7:17
2	13.9	5:19	7:14
3	13.8	5:22	7:11
4	13.7	5:25	7:08
5	13.6	5:27	7:04
6	13.5	5:30	7:01
7	13.4	5:32	6:58
8	13.3	5:35	6:55
9	13.2	5:37	6:51
10	13.1	5:40	6:48
11	13.0	5:42	6:45
12	12.9	5:45	6:42
13	12.8	5:47	6:38
14	12.8	5:50	6:35
15	12.7	5:52	6:32
16	12.6	5:55	6:28
17	12.5	5:57	6:25
18	12.4	6:00	6:22
19	12.3	6:03	6:19
20	12.2	6:05	6:15
21	12.1	6:08	6:12
22	12.0	6:10	6:09
23	11.9	6:13	6:05
24	11.8	6:15	6:02
25	11.7	6:18	5:59
26	11.6	6:20	5:56
27	11.5	6:23	5:52
28	11.4	6:26	5:49
29	11.3	6:28	5:46
30	11.2	6:31	5:43

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.21 kWh/m².

For context, solar energy here swings from a low near 0.12 kWh/m² to a high of 5.28 kWh/m² in June across the year — September's 2.21 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)	2.9	2.8	2.8	2.7	2.7	2.6	2.6	2.5	2.5	2.4	2.4	2.4	2.3	2.3	2.2	2.2	2.1	2.1	2.1	2.0	2.0	1.9	1.9	1.8	1.8	1.7	1.7	1.6	1.6	1.6
Level	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Dim	Dim	Dim	Dim	Dim	Dim	Dim	Dim	Dim	Dim

	Solar energy (kWh/m²)	Level
1	2.9	Moderate
2	2.8	Moderate
3	2.8	Moderate
4	2.7	Moderate
5	2.7	Moderate
6	2.6	Moderate
7	2.6	Moderate
8	2.5	Moderate
9	2.5	Moderate
10	2.4	Moderate
11	2.4	Moderate
12	2.4	Moderate
13	2.3	Moderate
14	2.3	Moderate
15	2.2	Moderate
16	2.2	Moderate
17	2.1	Moderate
18	2.1	Moderate
19	2.1	Moderate
20	2.0	Moderate
21	2.0	Dim
22	1.9	Dim
23	1.9	Dim
24	1.8	Dim
25	1.8	Dim
26	1.7	Dim
27	1.7	Dim
28	1.6	Dim
29	1.6	Dim
30	1.6	Dim

Planning a trip in September

Is September a good time to visit Lahti?

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

4.0

Sightseeing

5th-best month of the year

0.3

Beach & pool

5th-best month of the year

September is a reasonable time to visit Lahti for sightseeing.

What to pack for Lahti in September

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

In September, Lahti sees daytime highs around 14°C and nights near 7°C. Worth packing: a warm layer and rain gear. About 10 days see rain.

a warm layerrain gear

UV index in Lahti in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 2. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Lahti peaks around June 19 at about 5 (high) — a little sun protection helps at midday. It bottoms out near January 1 at about 0 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 4 months of the year.

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

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

Location & terrain

Where is Lahti?

Lahti sits at 61.0°N, 25.7°E, 105 m above sea level, in Finland. The nearest listed city is Hollola, 9.0 km away.

Topography around Lahti

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

Within 3 km, the terrain around Lahti has only modest variations in elevation — a maximum elevation change of 91 m around an average of 104 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 164 m; within 80 km, only modest variations in elevation — a maximum elevation change of 226 m.

The land around Lahti is covered by trees (51%) and artificial surfaces (35%) within 3 km, trees (65%) within 16 km, and trees (71%) within 80 km.

3 km

91 m

trees 51%

16 km

164 m

trees 65%

80 km

226 m

trees 71%

treesgrasslandcroplandartificial surfaceswater

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

September weather nearby: Hollola 9.0 km · Orimattila 20 km · Heinola 32 km · Mäntsälä 43 km · Riihimäki 55 km · Kouvola 58 km · Hyvinge 58 km · Janakkala 58 km

Finland travel facts

Travel advisory: Level 1; Exercise Normal Precautions
Power plugs: Type C / F; 230 V · 50 Hz
Prices: ≈ 85% of US; price level, 2025
GDP per capita: $56,149; 2025
Happiness: 7.8 / 10; World Happiness, 2025
Safe drinking water: 100%; of population, 2024
Homicide rate: 1; per 100k, 2023
Road deaths: 3.9; per 100k/yr, 2019
Income group: High; World Bank
English: Very high; EF EPI 603
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 Lahti (60.9827°, 25.6615°, elevation 105 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	17	10
2	17	10
3	17	9
4	17	9
5	16	9
6	16	9
7	16	9
8	16	9
9	16	9
10	15	8
11	15	8
12	15	8
13	15	8
14	15	8
15	14	7
16	14	7
17	14	7
18	14	7
19	14	7
20	13	7
21	13	6
22	13	6
23	13	6
24	13	6
25	12	6
26	12	6
27	12	6
28	12	6
29	11	5
30	11	5

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

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

	Dry (%)	Comfortable (%)	Humid (%)
1	80	19	1
2	82	17	1
3	83	16	1
4	84	15	1
5	85	14	1
6	88	12	0
7	89	11	0
8	90	10	0
9	90	10	0
10	91	9	0
11	92	8	0
12	93	7	0
13	93	7	0
14	94	6	0
15	95	5	0
16	95	5	0
17	96	4	0
18	96	4	0
19	97	3	0
20	97	3	0
21	98	2	0
22	98	2	0
23	98	2	0
24	99	1	0
25	99	1	0
26	99	1	0
27	99	1	0
28	99	1	0
29	99	1	0
30	99	1	0

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

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

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

	Dry (%)	Comfortable (%)	Humid (%)
1	80	19	1
2	82	17	1
3	83	16	1
4	84	15	1
5	85	14	1
6	88	12	0
7	89	11	0
8	90	10	0
9	90	10	0
10	91	9	0
11	92	8	0
12	93	7	0
13	93	7	0
14	94	6	0
15	95	5	0
16	95	5	0
17	96	4	0
18	96	4	0
19	97	3	0
20	97	3	0
21	98	2	0
22	98	2	0
23	98	2	0
24	99	1	0
25	99	1	0
26	99	1	0
27	99	1	0
28	99	1	0
29	99	1	0
30	99	1	0

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

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

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

	Dry (%)	Comfortable (%)	Humid (%)
1	80	19	1
2	82	17	1
3	83	16	1
4	84	15	1
5	85	14	1
6	88	12	0
7	89	11	0
8	90	10	0
9	90	10	0
10	91	9	0
11	92	8	0
12	93	7	0
13	93	7	0
14	94	6	0
15	95	5	0
16	95	5	0
17	96	4	0
18	96	4	0
19	97	3	0
20	97	3	0
21	98	2	0
22	98	2	0
23	98	2	0
24	99	1	0
25	99	1	0
26	99	1	0
27	99	1	0
28	99	1	0
29	99	1	0
30	99	1	0