Imperial Beach weather in September

In September, Imperial Beach sees average daytime highs of 73°F and overnight lows near 65°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.

Day-to-day highs hold fairly steady near 73°F through the month. The sky is clear or mostly clear about 82% 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 Imperial Beach's 1st-clearest and 10th-windiest month. For the whole year in context, see Imperial Beach's year-round climate.

Daytime high
73°
2nd warmest
Overnight low
65°
11th coldest
Rainfall
0.2 in
0.8 wet days
Daylight
12 h 12 min
5:37 AM – 5:49 PM
Cloud cover
23%
1st clearest
Wind
6 mph
10th windiest
Solar energy
6.18 kWh/m²
Travel score
9.0
out of 10

Imperial Beach is city in San Diego County, California, United States.

Density
2,360/km²
people per km²
Founded
1887

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 73°F through the month.

A typical September day in Imperial Beach reaches about 73°F in the afternoon and slips back to 65°F overnight — a 8°F spread between the day's warmth and the night's chill. On most days the high lands between 68°F and 78°F. Set against its neighbours, September runs on par with August and about 3°F warmer than October.

60°70°80°151015202530
Avg high (°F)Avg low (°F)
17467
27467
37467
47466
57466
67466
77466
87466
97366
107366
117366
127365
137365
147365
157365
167365
177365
187365
197365
207365
217365
227364
237364
247364
257364
267264
277264
287264
297264
307264

Imperial Beach 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
Jan61° / 52°2.56.110.15.8
Feb61° / 52°3.1710.85.4
Mar61° / 53°2.15.911.85.8
Apr63° / 55°1.04.212.86.7
May65° / 58°0.42.113.67.5
Jun68° / 60°0.10.414.18.3
Jul72° / 65°0.10.413.98.8
Aug74° / 66°0.00.313.29.2
Sep73° / 65°0.20.812.29.0
Oct70° / 62°0.62.411.28.3
Nov66° / 56°1.03.610.37.4
Dec61° / 52°2.05.79.96.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 82% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 11% of September, with mostly cloudy or overcast conditions the remaining 7%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1955
2955
3955
4955
5955
6955
7955
8955
9955
10955
11955
12955
13955
14955
15946
16937
17937
18928
19928
20928
21928
22919
239010
249010
259010
268911
278911
288911
298812
308812

Chance of precipitation in September

Any precipitation

Imperial Beach 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 5% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
11
21
31
41
51
61
72
82
92
102
112
122
132
142
153
163
173
183
193
203
213
224
234
244
254
264
274
284
294
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 40% of days. Sticky, muggy-or-worse air turns up on roughly 11% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
11265320
22275120
32284920
42304820
52314620
63334519
73344419
84354318
94374217
105384116
115394115
126404013
136424012
147423911
157433910
16844399
17844399
18944398
19944397
201044397
211044396
221144396
231244395
241245385
251345374
261445364
271645354
281746343
291946323
302047303

Wind in September

Winds average 6 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
286calm
296calm
306calm

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 5:27 AM to 5:46 AM, and sunset from 6:09 PM to 5:29 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:276:09
212.75:286:08
312.65:286:07
412.65:296:05
512.65:306:04
612.55:306:03
712.55:316:01
812.55:326:00
912.45:325:58
1012.45:335:57
1112.45:345:56
1212.35:345:54
1312.35:355:53
1412.35:365:52
1512.25:365:50
1612.25:375:49
1712.25:385:47
1812.15:385:46
1912.15:395:44
2012.15:395:43
2112.05:405:42
2212.05:415:40
2312.05:415:39
2411.95:425:38
2511.95:435:36
2611.95:445:35
2711.85:445:33
2811.85:455:32
2911.85:465:31
3011.75:465:29

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.18 kWh/m².

For context, solar energy here swings from a low near 3.16 kWh/m² to a high of 7.97 kWh/m² in June across the year — September's 6.18 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.7Intense
26.7Intense
36.7Intense
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
265.8Bright
275.7Bright
285.7Bright
295.6Bright
305.6Bright
Planning a trip in September

Is September a good time to visit Imperial Beach?

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

9.0
Sightseeing
2nd-best month of the year
6.8
Beach & pool
2nd-best month of the year

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

What to pack for Imperial Beach in September

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

In September, Imperial Beach sees daytime highs around 73°F and nights near 65°F. Pack sun protection. Worth having: light clothes.

sun protectionlight clothes

Sea temperature near Imperial Beach in September

The nearest coast averages about 69°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 February near 59°F.

It's comfortable for a long swim from Jul 13 to Sep 28 — about 2.6 months when the water holds above 68°F.

60°65°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingcomfortable to swim
Sea temperature (°F)Comfort
Jan60Cool
Feb59Cool
Mar60Cool
Apr61Cool
May63Cool
Jun65Cool
Jul68Refreshing
Aug70Refreshing
Sep69Refreshing
Oct67Cool
Nov64Cool
Dec61Cool

UV index in Imperial Beach 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 Imperial Beach peaks around June 23 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 — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJun 23UV 11Dec 17UV 3
UV index (midday)Level
Jan4Moderate
Feb5Moderate
Mar5High
Apr8Very high
May8Very high
Jun11Extreme
Jul11Extreme
Aug10Extreme
Sep8Very high
Oct6High
Nov4Moderate
Dec3Moderate

Air quality in Imperial Beach 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 Imperial Beach is worst in October — around 33 µg/m³ PM2.5 (moderate), about 5.4× the cleanest month (May, 6 µg/m³).

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

010203040JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateOct 1631 µg/m³May 176 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb11Good
Mar10Good
Apr9Good
May6Good
Jun9Good
Jul8Good
Aug9Good
Sep16Moderate
Oct33Moderate
Nov13Moderate
Dec17Moderate
Location & terrain

Where is Imperial Beach?

Imperial Beach sits at 32.6°N, 117.1°W, 20 ft above sea level, in United States. The nearest listed city is Chula Vista, 4.3 mi away.

Topography around Imperial Beach

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

Within 2 miles, the terrain around Imperial Beach has only modest variations in elevation — a maximum elevation change of 105 ft around an average of 16 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,152 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 6,450 ft.

The land around Imperial Beach is covered by artificial surfaces (36%) and water (35%) within 2 miles, water (43%) and artificial surfaces (35%) within 10 miles, and water (35%) and shrubs (24%) within 50 miles.

2 miles
105 ft
10 miles
1,152 ft
50 miles
6,450 ft
treesshrubsgrasslandartificial surfacesbare terrainwaterwetland
September weather nearby: Chula Vista 4.3 mi · National City 6.8 mi · Coronado 8.1 mi · Tijuana 8.7 mi · San Diego 9.3 mi · Pórticos de San Antonio 11 mi · La Presa 11 mi · La Joya 12 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 Imperial Beach (32.5839°, -117.1131°, elevation 20 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).