Carlsbad weather in September

In September, Carlsbad sees average daytime highs of 81°F and overnight lows near 64°F, with 0.1 in of rain across 0.7 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 83% 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 Carlsbad's 2nd-clearest and 11th-windiest month. For the whole year in context, see Carlsbad's year-round climate.

Daytime high
81°
2nd warmest
Overnight low
64°
10th coldest
Rainfall
0.1 in
0.7 wet days
Daylight
12 h 12 min
5:38 AM – 5:50 PM
Cloud cover
19%
2nd clearest
Wind
4 mph
11th windiest
Solar energy
6.16 kWh/m²
Travel score
8.6
out of 10

Carlsbad is coastal city in the North County region of San Diego County, California, United States.

Density
1,133/km²
people per km²
Founded
1952

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 Carlsbad 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 73°F and 89°F. Set against its neighbours, September runs about 1°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
88266
98265
108165
118165
128165
138165
148165
158164
168064
178064
188064
198064
208064
218064
228064
238063
248063
258063
268063
278063
288063
297962
307962

Carlsbad 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
Jan64° / 47°2.95.810.16.7
Feb64° / 48°3.66.810.86.4
Mar65° / 50°2.26.211.76.8
Apr68° / 53°1.14.112.87.5
May71° / 56°0.52.113.78.1
Jun75° / 60°0.10.514.19.1
Jul80° / 65°0.10.4148.8
Aug82° / 66°0.00.213.28.5
Sep81° / 64°0.10.712.28.6
Oct76° / 59°0.72.611.28.7
Nov70° / 52°1.13.510.37.9
Dec64° / 47°2.15.19.86.8

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 83% 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 10%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1946
2937
3946
4946
5946
6946
7946
8937
9937
10937
11937
12928
13928
14919
15919
169010
179010
189010
198911
208911
218911
228812
238713
248713
258713
268614
278614
288614
298614
308614

Chance of precipitation in September

Any precipitation

Carlsbad gets around 0.1 in of rain over 0.7 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 3% and peaks near 5% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
10
20
31
41
51
61
71
81
92
102
112
122
132
143
153
163
173
183
194
204
214
224
234
244
254
264
274
284
295
305

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 41% of days. Sticky, muggy-or-worse air turns up on roughly 15% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
122247282
222346272
322445272
422544262
532644262
632843252
732943241
843043231
943143211
1043243201
1153343180
1253443170
1363543160
1463643140
1573743130
1673843120
1783843110
1893943100
199394390
2010394290
2111394280
2211404180
2312404070
2413404070
2514413860
2616413760
2717413660
2819413550
2921413350
3023423240

Wind in September

Winds average 4 mph in September.

Across September, daily wind ranges from about 3 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
13calm
23calm
33calm
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 5:47 AM, and sunset from 6:11 PM to 5:30 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:286:11
212.75:286:09
312.75:296:08
412.65:306:07
512.65:306:05
612.55:316:04
712.55:326:02
812.55:326:01
912.45:336:00
1012.45:345:58
1112.45:345:57
1212.35:355:55
1312.35:365:54
1412.35:365:53
1512.25:375:51
1612.25:385:50
1712.25:385:48
1812.15:395:47
1912.15:405:46
2012.15:405:44
2112.05:415:43
2212.05:425:41
2312.05:425:40
2411.95:435:38
2511.95:445:37
2611.95:455:36
2711.85:455:34
2811.85:465:33
2911.75:475:31
3011.75:475:30

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.16 kWh/m².

For context, solar energy here swings from a low near 3.08 kWh/m² to a high of 7.96 kWh/m² in June across the year — September's 6.16 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.7Intense
26.7Intense
36.6Intense
46.6Intense
56.6Intense
66.5Intense
76.5Intense
86.5Intense
96.4Intense
106.4Intense
116.4Intense
126.3Intense
136.3Intense
146.3Intense
156.2Intense
166.2Intense
176.1Intense
186.1Intense
196.0Intense
206.0Intense
216.0Bright
225.9Bright
235.9Bright
245.8Bright
255.8Bright
265.7Bright
275.7Bright
285.7Bright
295.6Bright
305.6Bright
Planning a trip in September

Is September a good time to visit Carlsbad?

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

8.6
Sightseeing
4th-best month of the year
8.8
Beach & pool
2nd-best month of the year

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

What to pack for Carlsbad in September

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

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

light clothessun protection

Sea temperature near Carlsbad 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 71°F and coldest in January near 59°F.

It's comfortable for a long swim from Jul 5 to Oct 7 — 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
May64Cool
Jun66Cool
Jul69Refreshing
Aug71Refreshing
Sep70Refreshing
Oct67Cool
Nov64Cool
Dec61Cool

UV index in Carlsbad in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Carlsbad peaks around July 11 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 17 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 highHighModerateJul 11UV 11Dec 17UV 3
UV index (midday)Level
Jan4Moderate
Feb5Moderate
Mar5Moderate
Apr8Very high
May8Very high
Jun11Extreme
Jul11Extreme
Aug10Extreme
Sep8Very high
Oct6High
Nov4Moderate
Dec3Moderate

Air quality in Carlsbad 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 Carlsbad is worst in September — around 26 µg/m³ PM2.5 (moderate), about 3.4× the cleanest month (May, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateSep 1625 µg/m³May 168 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb12Moderate
Mar12Moderate
Apr11Good
May8Good
Jun11Good
Jul11Good
Aug15Moderate
Sep26Moderate
Oct14Moderate
Nov12Moderate
Dec16Moderate
Location & terrain

Where is Carlsbad?

Carlsbad sits at 33.2°N, 117.4°W, 52 ft above sea level, in United States. The nearest listed city is Oceanside, 3.1 mi away.

Topography around Carlsbad

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

Within 2 miles, the terrain around Carlsbad has only modest variations in elevation — a maximum elevation change of 344 ft around an average of 56 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,335 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 6,624 ft.

The land around Carlsbad is covered by water (48%) and artificial surfaces (37%) within 2 miles, water (47%) and artificial surfaces (24%) within 10 miles, and water (33%) and shrubs (21%) within 50 miles.

2 miles
344 ft
10 miles
1,335 ft
50 miles
6,624 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: Oceanside 3.1 mi · Vista 6.8 mi · Encinitas 9.3 mi · San Marcos 11 mi · Escondido 16 mi · Fallbrook 16 mi · Rancho Penasquitos 19 mi · Mira Mesa 21 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 Carlsbad (33.1581°, -117.3506°, elevation 52 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).