Isernia weather in September

In September, Isernia sees average daytime highs of 22°C and overnight lows near 13°C, with 79 mm of rain across 10.4 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 24°C in the first days to 20°C by the end. The sky is clear or mostly clear about 41% 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 Isernia's 4th-clearest and 9th-windiest month. For the whole year in context, see Isernia's year-round climate.

Daytime high
22°
4th warmest
Overnight low
13°
9th coldest
Rainfall
79 mm
10.4 wet days
Daylight
12 h 18 min
5:49 AM – 6:06 PM
Cloud cover
49%
4th clearest
Wind
5 km/h
9th windiest
Solar energy
4.47 kWh/m²
Travel score
6.8
out of 10
Air quality
Excellent
PM10 11.9 µg/m³ · 2018

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 24°C in the first days to 20°C by the end.

A typical September day in Isernia reaches about 22°C in the afternoon and slips back to 13°C overnight — a 10°C spread between the day's warmth and the night's chill. On most days the high lands between 19°C and 26°C. Set against its neighbours, September runs about 4°C cooler than August and about 4°C warmer than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12515
22514
32414
42414
52414
62414
72414
82313
92313
102313
112313
122313
132313
142313
152213
162213
172212
182212
192212
202212
212212
222112
232112
242112
252111
262111
272111
282011
292011
302011

How September really feels in Isernia

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.

Isernia weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / 8810.62.49.31.3
Feb / 9211.12.810.31.6
Mar12° / 10612.92.211.72.9
Apr15° / 10814.20.313.14.1
May19° / 10°8912.9014.35.8
Jun24° / 14°6210.20157.1
Jul26° / 16°438.3014.77.4
Aug27° / 16°368.3013.77.3
Sep22° / 13°7910.4012.36.8
Oct18° / 11110.40.110.95.8
Nov13° / 15012.50.89.73.4
Dec / 12112.42.491.7

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 41% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 23% of September, with mostly cloudy or overcast conditions the remaining 37%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17525
27426
37228
47228
57030
66931
76832
86733
96535
106535
116337
126337
136238
146139
156139
166139
176040
186040
195941
205941
215941
226040
235941
245941
255941
265941
275842
285842
295842
305842

Chance of precipitation in September

Any precipitation

Isernia gets around 79 mm of rain over 10.4 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 35% and peaks near 36% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
133
234
334
435
535
636
736
836
936
1036
1136
1236
1336
1436
1536
1636
1736
1835
1935
2035
2135
2234
2334
2433
2533
2633
2733
2833
2933
3033

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 47% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
12642293
22843273
33043252
43143232
53344212
63544191
73645181
83745161
93846151
103946141
114046141
124145131
134245131
144344121
154543120
164642110
174841110
185040100
195238100
20543790
21553690
22573580
23593470
24603370
25623260
26633160
27653050
28663040
29682930
30692830

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 5:33 AM to 6:04 AM, and sunset from 6:32 PM to 5:41 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:336:32
212.95:346:30
312.95:356:29
412.85:376:27
512.85:386:25
612.75:396:23
712.75:406:22
812.75:416:20
912.65:426:18
1012.65:436:16
1112.55:446:15
1212.55:456:13
1312.45:466:11
1412.45:476:09
1512.35:486:07
1612.35:496:06
1712.25:506:04
1812.25:516:02
1912.15:526:00
2012.15:535:58
2112.05:545:57
2212.05:565:55
2311.95:575:53
2411.95:585:51
2511.85:595:49
2611.86:005:48
2711.76:015:46
2811.76:025:44
2911.76:035:42
3011.66:045:41

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.47 kWh/m².

For context, solar energy here swings from a low near 1.66 kWh/m² to a high of 6.8 kWh/m² in July across the year — September's 4.47 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.2Bright
35.1Bright
45.1Bright
55.0Bright
65.0Bright
74.9Bright
84.8Bright
94.8Bright
104.7Bright
114.7Bright
124.6Bright
134.6Bright
144.5Bright
154.5Bright
164.5Bright
174.4Bright
184.3Bright
194.3Bright
204.3Bright
214.2Bright
224.2Bright
234.1Bright
244.1Bright
254.0Bright
264.0Moderate
273.9Moderate
283.9Moderate
293.9Moderate
303.8Moderate
Planning a trip in September

Is September a good time to visit Isernia?

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

6.8
Sightseeing
4th-best month of the year
4.9
Beach & pool
4th-best month of the year

September is a reasonable time to visit Isernia for sightseeing.

What to pack for Isernia in September

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

In September, Isernia sees daytime highs around 22°C and nights near 13°C. Worth packing: light clothes and rain gear. About 10 days see rain.

light clothesrain gear

Sea temperature near Isernia in September

The nearest coast averages about 24°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 60 km away) is warmest in August at about 26°C and coldest in February near 14°C.

It's comfortable for a long swim from May 27 to Nov 5 — about 5.4 months when the water holds above 20°C.

15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan15Bracing
Feb14Bracing
Mar14Bracing
Apr16Cool
May19Cool
Jun22Refreshing
Jul25Warm
Aug26Warm
Sep24Warm
Oct22Refreshing
Nov19Cool
Dec17Cool

UV index in Isernia 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 Isernia peaks around July 15 at about 10 (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 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 15UV 10Dec 21UV 1
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5High
Apr5Moderate
May7Very high
Jun9Very high
Jul10Extreme
Aug9Very high
Sep6High
Oct4Moderate
Nov2Moderate
Dec1Low

Air quality in Isernia 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 Isernia is worst in April — around 22 µg/m³ PM2.5 (moderate), and holds fairly steady the rest of the year.

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateApr 1021 µg/m³Sep 1714 µg/m³
PM2.5 (µg/m³)Level
Jan19Moderate
Feb20Moderate
Mar21Moderate
Apr22Moderate
May18Moderate
Jun16Moderate
Jul16Moderate
Aug16Moderate
Sep14Moderate
Oct16Moderate
Nov16Moderate
Dec17Moderate
Location & terrain

Where is Isernia?

Isernia sits at 41.6°N, 14.2°E, 423 m above sea level, in Italy. The nearest listed city is Cassino, 36 km away.

Topography around Isernia

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

Within 3 km, the terrain around Isernia has significant variations in elevation — a maximum elevation change of 398 m around an average of 468 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,340 m; within 80 km, extreme variations in elevation — a maximum elevation change of 2,771 m.

The land around Isernia is covered by trees (63%) within 3 km, trees (72%) and grassland (22%) within 16 km, and trees (51%) and cropland (21%) within 80 km.

3 km
398 m
16 km
1,340 m
80 km
2,771 m
treesshrubsgrasslandcroplandartificial surfaceswater
September weather nearby: Cassino 36 km · Campobasso 36 km · Sora 53 km · Capua 55 km · Minturno 55 km · Sulmona 57 km · Santa Maria Capua Vetere 57 km · Caserta 59 km

Italy travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F / L
230 V · 50 Hz
Prices
≈ 69% of US
price level, 2025
GDP per capita
$43,309
2025
Happiness
6.6 / 10
World Happiness, 2025
Safe drinking water
97%
of population, 2024
Homicide rate
0.6
per 100k, 2023
Road deaths
5.3
per 100k/yr, 2019
Income group
High
World Bank
English
Moderate
EF EPI 513
Religion
Christian 81%unaffiliated 13%Muslim 5%other 1%

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 Isernia (41.596°, 14.234°, elevation 423 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).