San Clemente weather in September

In September, San Clemente sees average daytime highs of 81°F and overnight lows near 64°F, with 0.2 in of rain across 0.8 wet days and about 12.2 hours of daylight. It is the 2nd-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 83°F in the first days to 79°F by the end. The sky is clear or mostly clear about 85% of the time in September, and the air most often feels humid.

Daylight stretches from about 12 h 42 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is San Clemente's 2nd-clearest and 10th-windiest month. For the whole year in context, see San Clemente's year-round climate.

Daytime high
81°
2nd warmest
Overnight low
64°
10th coldest
Rainfall
0.2 in
0.8 wet days
Daylight
12 h 12 min
5:39 AM – 5:51 PM
Cloud cover
18%
2nd clearest
Wind
4 mph
10th windiest
Solar energy
6.08 kWh/m²
Travel score
8.7
out of 10

San Clemente is city in Orange County, California, United States.

Density
1,300/km²
people per km²
Founded
1928

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 83°F in the first days to 79°F by the end.

A typical September day in San Clemente reaches about 81°F in the afternoon and slips back to 64°F overnight — a 16°F spread between the day's warmth and the night's chill. On most days the high lands between 72°F and 89°F. Set against its neighbours, September runs about 2°F cooler than August and about 5°F warmer than October.

50°60°70°80°90°151015202530
Avg high (°F)Avg low (°F)
18366
28366
38366
48266
58266
68266
78266
88265
98165
108165
118165
128165
138165
148164
158064
168064
178064
188064
198064
208064
218064
228064
238063
248063
258063
268063
277963
287963
297962
307962

San Clemente weather by month

How September compares with the rest of the year at a glance. September is the 2nd-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan63° / 47°3.15.9106.4
Feb63° / 48°3.76.810.86.2
Mar65° / 50°2.16.211.76.7
Apr68° / 53°0.93.312.87.6
May71° / 56°0.4213.78.2
Jun75° / 60°0.10.414.29.2
Jul80° / 65°0.10.4148.8
Aug82° / 66°0.10.213.28.4
Sep81° / 64°0.20.812.28.7
Oct76° / 59°0.72.611.28.7
Nov69° / 52°1.03.210.37.9
Dec63° / 47°2.24.99.86.6

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 85% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 7% of September, with mostly cloudy or overcast conditions the remaining 8%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1946
2946
3946
4946
5946
6946
7946
8946
9946
10946
11946
12937
13928
14928
15928
16928
17928
18928
19928
20919
219010
229010
239010
248911
258911
268911
278911
288911
298911
308911

Chance of precipitation in September

Any precipitation

San Clemente gets around 0.2 in of rain over 0.8 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 3% and peaks near 4% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
11
21
31
42
52
62
72
82
92
102
112
122
132
142
152
163
173
183
193
203
213
223
233
243
254
264
274
284
294
304

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the humid band about 44% of days. Sticky, muggy-or-worse air turns up on roughly 11% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
12255419
22265319
33275119
43285019
53304819
64314718
74324717
85334616
95344615
106344514
116354513
127364512
138364511
148374410
15937449
161038449
171038448
181138448
191238447
201237437
211337437
221337436
231438426
241538416
251638405
261739395
271839385
282039374
292140354
302340334

Wind in September

Winds average 4 mph in September.

Across September, daily wind ranges from about 4 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 42 min at the start of September to 11 h 42 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 60 minutes over September. Sunrise moves from 5:28 AM to 5:49 AM, and sunset from 6:12 PM to 5:31 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:286:12
212.75:296:11
312.75:306:09
412.65:306:08
512.65:316:06
612.65:326:05
712.55:326:04
812.55:336:02
912.55:346:01
1012.45:355:59
1112.45:355:58
1212.35:365:57
1312.35:375:55
1412.35:375:54
1512.25:385:52
1612.25:395:51
1712.25:395:49
1812.15:405:48
1912.15:415:47
2012.15:415:45
2112.05:425:44
2212.05:435:42
2312.05:445:41
2411.95:445:39
2511.95:455:38
2611.85:465:37
2711.85:465:35
2811.85:475:34
2911.75:485:32
3011.75:495:31

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.08 kWh/m².

For context, solar energy here swings from a low near 3.01 kWh/m² to a high of 7.82 kWh/m² in June across the year — September's 6.08 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.7Intense
26.6Intense
36.6Intense
46.6Intense
56.5Intense
66.5Intense
76.4Intense
86.4Intense
96.4Intense
106.3Intense
116.3Intense
126.2Intense
136.2Intense
146.2Intense
156.1Intense
166.1Intense
176.0Intense
186.0Bright
196.0Bright
205.9Bright
215.9Bright
225.8Bright
235.8Bright
245.7Bright
255.7Bright
265.6Bright
275.6Bright
285.5Bright
295.5Bright
305.5Bright
Planning a trip in September

Is September a good time to visit San Clemente?

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

8.7
Sightseeing
3rd-best month of the year
8.8
Beach & pool
3rd-best month of the year

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

What to pack for San Clemente in September

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

In September, San Clemente sees daytime highs around 81°F and nights near 64°F. Pack light clothes and sun protection.

light clothessun protection

Sea temperature near San Clemente in September

The nearest coast averages about 70°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in August at about 70°F and coldest in January near 59°F.

It's comfortable for a long swim from Jul 6 to Oct 6 — about 3.1 months when the water holds above 68°F.

60°65°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingcomfortable to swim
Sea temperature (°F)Comfort
Jan59Cool
Feb59Cool
Mar60Cool
Apr61Cool
May63Cool
Jun66Cool
Jul69Refreshing
Aug70Refreshing
Sep70Refreshing
Oct67Cool
Nov64Cool
Dec61Cool

UV index in San Clemente in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Clemente peaks around June 23 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateVery highExtremeVery highHighModerateJun 23UV 10Dec 16UV 3
UV index (midday)Level
Jan4Moderate
Feb5Moderate
Mar5Moderate
Apr8Very high
May8Very high
Jun11Extreme
Jul10Extreme
Aug10Extreme
Sep8Very high
Oct6High
Nov3Moderate
Dec3Moderate

Air quality in San Clemente 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 San Clemente is worst in September — around 49 µg/m³ PM2.5 (poor), about 4.0× the cleanest month (May, 12 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecModeratePoorModerateSep 1447 µg/m³May 1713 µg/m³
PM2.5 (µg/m³)Level
Jan18Moderate
Feb19Moderate
Mar19Moderate
Apr17Moderate
May12Moderate
Jun17Moderate
Jul19Moderate
Aug32Moderate
Sep49Poor
Oct21Moderate
Nov21Moderate
Dec18Moderate
Location & terrain

Where is San Clemente?

San Clemente sits at 33.4°N, 117.6°W, 233 ft above sea level, in United States. The nearest listed city is Dana Point, 5.6 mi away.

Topography around San Clemente

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of San Clemente.

Within 2 miles, the terrain around San Clemente has significant variations in elevation — a maximum elevation change of 886 ft around an average of 236 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,280 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 6,109 ft.

The land around San Clemente is covered by artificial surfaces (35%), water (27%) and trees (21%) within 2 miles, water (44%) within 10 miles, and water (36%) and artificial surfaces (22%) within 50 miles.

2 miles
886 ft
10 miles
2,280 ft
50 miles
6,109 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Dana Point 5.6 mi · San Juan Capistrano 6.2 mi · Laguna Niguel 8.7 mi · Ladera Ranch 9.9 mi · Aliso Viejo 12 mi · Mission Viejo 12 mi · Laguna Beach 12 mi · Laguna Hills 14 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

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 San Clemente (33.427°, -117.612°, elevation 233 ft), 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).