Viterbo weather in September

In September, Viterbo sees average daytime highs of 25°C and overnight lows near 16°C, with 84 mm of rain across 9.1 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 27°C in the first days to 23°C by the end. The sky is clear or mostly clear about 52% of the time in September, and the air most often feels comfortable.

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 Viterbo's 4th-clearest and 8th-windiest month. For the whole year in context, see Viterbo's year-round climate.

Daytime high
25°
4th warmest
Overnight low
16°
9th coldest
Rainfall
84 mm
9.1 wet days
Daylight
12 h 18 min
5:57 AM – 6:14 PM
Cloud cover
42%
4th clearest
Wind
9 km/h
8th windiest
Solar energy
4.52 kWh/m²
Travel score
7.1
out of 10
Air quality
Moderate
PM2.5 11.3 µg/m³ · 2019

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 27°C in the first days to 23°C by the end.

A typical September day in Viterbo reaches about 25°C in the afternoon and slips back to 16°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 21°C and 28°C. Set against its neighbours, September runs about 5°C cooler than August and about 5°C warmer than October.

10°15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
12717
22717
32717
42717
52717
62617
72617
82616
92616
102616
112616
122516
132516
142516
152516
162516
172415
182415
192415
202415
212415
222415
232315
242315
252314
262314
272314
282314
292214
302214

How September really feels in Viterbo

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.

Viterbo weather by month

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

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan10° / 618.20.59.32.2
Feb11° / 688.70.810.32.8
Mar14° / 749.20.511.64.3
Apr17° / 7611.10.113.15.5
May22° / 12°639.4014.46.9
Jun26° / 16°4670157.4
Jul30° / 19°284.8014.86.4
Aug30° / 19°336013.76.1
Sep25° / 16°849.1012.37.1
Oct20° / 12°11410.6010.86.4
Nov14° / 12712.10.19.64.1
Dec11° / 8610.10.492.5

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 52% 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 30%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
18119
28020
37822
47822
57723
67624
77525
87426
97327
107327
117228
127030
137030
146931
156931
166832
176733
186733
196634
206634
216634
226634
236634
246634
256634
266535
276535
286535
296535
306535

Chance of precipitation in September

Any precipitation

Viterbo gets around 84 mm of rain over 9.1 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 31% and peaks near 34% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
126
227
327
427
528
628
729
829
930
1031
1131
1232
1332
1433
1533
1634
1734
1834
1934
2034
2133
2233
2332
2432
2532
2632
2731
2832
2932
3032

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels comfortable — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the comfortable band about 31% of days. Sticky, muggy-or-worse air turns up on roughly 9% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
117293419
218303418
319303417
420313315
521313314
622323313
722323312
823323412
923323411
1024313411
1124313411
1225313410
1325303410
1426303410
1527303410
162829339
172929339
183029329
193129328
203329318
213429307
223529297
233630286
243731276
253732265
263833254
273934244
283934233
294035223
304036213

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 8 km/h on the calmest days to 9 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
59calm
69calm
79calm
89calm
99calm
109calm
119calm
129calm
139calm
149calm
159calm
169calm
179calm
189calm
199calm
209calm
219calm
229calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

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 5:41 AM to 6:13 AM, and sunset from 6:42 PM to 5:49 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:416:42
213.05:426:40
312.95:436:38
412.95:446:36
512.85:456:34
612.85:466:33
712.75:486:31
812.75:496:29
912.65:506:27
1012.65:516:25
1112.55:526:24
1212.55:536:22
1312.45:546:20
1412.45:556:18
1512.35:566:16
1612.35:576:14
1712.25:596:13
1812.26:006:11
1912.16:016:09
2012.16:026:07
2112.06:036:05
2212.06:046:03
2311.96:056:01
2411.96:066:00
2511.86:075:58
2611.86:095:56
2711.76:105:54
2811.76:115:52
2911.66:125:51
3011.66:135:49

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.52 kWh/m².

For context, solar energy here swings from a low near 1.57 kWh/m² to a high of 7.06 kWh/m² in July across the year — September's 4.52 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.4Bright
25.3Bright
35.2Bright
45.2Bright
55.1Bright
65.0Bright
75.0Bright
84.9Bright
94.9Bright
104.8Bright
114.7Bright
124.7Bright
134.6Bright
144.6Bright
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
293.8Moderate
303.8Moderate
Planning a trip in September

Is September a good time to visit Viterbo?

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

7.1
Sightseeing
2nd-best month of the year
6.3
Beach & pool
4th-best month of the year

September is one of the better times to visit Viterbo for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Viterbo in September

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

In September, Viterbo sees daytime highs around 25°C and nights near 16°C. Worth packing: light clothes, rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

Sea temperature near Viterbo 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 40 km away) is warmest in August at about 25°C and coldest in February near 14°C.

It's comfortable for a long swim from Jun 2 to Oct 31 — about 5 months when the water holds above 20°C.

15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan15Bracing
Feb14Bracing
Mar14Bracing
Apr15Cool
May18Cool
Jun22Refreshing
Jul24Warm
Aug25Warm
Sep23Refreshing
Oct21Refreshing
Nov19Cool
Dec16Cool

UV index in Viterbo in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Viterbo peaks around July 14 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 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 14UV 9Dec 23UV 1
UV index (midday)Level
Jan1Low
Feb3Moderate
Mar5Moderate
Apr5Moderate
May7High
Jun9Very high
Jul9Very high
Aug8Very high
Sep5High
Oct3Moderate
Nov2Moderate
Dec1Low
Location & terrain

Where is Viterbo?

Viterbo sits at 42.4°N, 12.1°E, 326 m above sea level, in Italy. The nearest listed city is Civitavecchia, 44 km away.

Topography around Viterbo

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

Within 3 km, the terrain around Viterbo has significant variations in elevation — a maximum elevation change of 280 m around an average of 352 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 1,009 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,182 m.

The land around Viterbo is covered by trees (51%) and artificial surfaces (24%) within 3 km, trees (57%) and cropland (27%) within 16 km, and trees (47%) and cropland (20%) within 80 km.

3 km
280 m
16 km
1,009 m
80 km
2,182 m
treesshrubsgrasslandcroplandartificial surfaceswater
September weather nearby: Civitavecchia 44 km · Terni 47 km · Todi 47 km · Cerveteri 48 km · Ladispoli 52 km · Monterotondo 59 km · Mentana 62 km · Rieti 62 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 Viterbo (42.4194°, 12.1056°, elevation 326 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. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).