La Mesa weather in September

In September, La Mesa sees average daytime highs of 80°F and overnight lows near 64°F, with 0.2 in of rain across 0.9 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 81°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 comfortable.

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 La Mesa's 2nd-clearest and 12th-windiest month. For the whole year in context, see La Mesa's year-round climate.

Daytime high
80°
2nd warmest
Overnight low
64°
11th coldest
Rainfall
0.2 in
0.9 wet days
Daylight
12 h 12 min
5:36 AM – 5:48 PM
Cloud cover
18%
2nd clearest
Wind
4 mph
12th windiest
Solar energy
6.24 kWh/m²
Travel score
8.8
out of 10

La Mesa is city in San Diego County, California, United States.

Density
2,545/km²
people per km²
Founded
1912

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 81°F in the first days to 79°F by the end.

A typical September day in La Mesa reaches about 80°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 88°F. Set against its neighbours, September runs on par with August and about 4°F warmer than October.

50°60°70°80°90°151015202530
Avg high (°F)Avg low (°F)
18266
28266
38266
48166
58165
68165
78165
88165
98165
108065
118065
128064
138064
148064
158064
168064
178064
187964
197963
207963
217963
227963
237963
247963
257963
267962
277962
287962
297962
307862

La Mesa 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° / 48°2.35.610.16.8
Feb64° / 48°2.9710.86.3
Mar65° / 50°1.95.811.86.8
Apr68° / 53°0.93.912.87.6
May70° / 56°0.4213.78.2
Jun74° / 60°0.10.614.19.2
Jul79° / 64°0.10.713.98.9
Aug81° / 65°0.10.513.28.7
Sep80° / 64°0.20.912.28.8
Oct76° / 59°0.62.511.28.7
Nov70° / 53°0.93.310.37.9
Dec64° / 48°1.95.29.96.8

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 9%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1955
2955
3955
4946
5946
6946
7946
8946
9946
10946
11937
12937
13937
14937
15937
16928
17919
18919
19919
209010
219010
228911
238911
248911
258911
268812
278713
288713
298713
308713

Chance of precipitation in September

Any precipitation

La Mesa gets around 0.2 in of rain over 0.9 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 (%)
13
23
33
43
53
63
73
83
93
103
113
123
133
143
153
163
174
184
194
204
214
224
234
244
254
264
274
284
294
304

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 46% of days. Sticky, muggy-or-worse air turns up on roughly 8% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
16384314
26384114
37394015
47403815
58413614
68423514
79433414
810443213
911453113
1012463112
1113473011
1214472910
131548289
141649278
151749267
161850267
171950256
182050255
192050255
202149254
212249254
222349254
232448253
242448243
252548233
262748233
272848223
282947213
293147202
303346192

Wind in September

Winds average 4 mph in September, the calmest month.

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 5:27 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
212.75:276:08
312.65:286:06
412.65:296:05
512.65:296:04
612.55:306:02
712.55:316:01
812.55:316:00
912.45:325:58
1012.45:325:57
1112.45:335:55
1212.35:345:54
1312.35:345:53
1412.35:355:51
1512.25:365:50
1612.25:365:48
1712.25:375:47
1812.15:385:46
1912.15:385:44
2012.15:395:43
2112.05:405:41
2212.05:405:40
2312.05:415:39
2411.95:425:37
2511.95:425:36
2611.95:435:34
2711.85:445:33
2811.85:455:32
2911.75:455:30
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 6.24 kWh/m².

For context, solar energy here swings from a low near 3.14 kWh/m² to a high of 8.08 kWh/m² in June across the year — September's 6.24 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.8Intense
26.8Intense
36.7Intense
46.7Intense
56.6Intense
66.6Intense
76.6Intense
86.5Intense
96.5Intense
106.5Intense
116.4Intense
126.4Intense
136.4Intense
146.3Intense
156.3Intense
166.2Intense
176.2Intense
186.2Intense
196.1Intense
206.1Intense
216.0Intense
226.0Bright
235.9Bright
245.9Bright
255.8Bright
265.8Bright
275.8Bright
285.7Bright
295.7Bright
305.6Bright
Planning a trip in September

Is September a good time to visit La Mesa?

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

8.8
Sightseeing
3rd-best month of the year
8.6
Beach & pool
2nd-best month of the year

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

What to pack for La Mesa in September

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

In September, La Mesa sees daytime highs around 80°F and nights near 64°F. Pack sun protection. Worth having: light clothes.

sun protectionlight clothes

Sea temperature near La Mesa 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 at the nearest coast (about 12 mi away) 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 La Mesa 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 La Mesa 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 — in 11 months 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 La Mesa 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 La Mesa 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 La Mesa?

La Mesa sits at 32.8°N, 117.0°W, 528 ft above sea level, in United States. The nearest listed city is Lemon Grove, 1.9 mi away.

Topography around La Mesa

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

Within 2 miles, the terrain around La Mesa has only modest variations in elevation — a maximum elevation change of 709 ft around an average of 551 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,549 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 6,450 ft.

The land around La Mesa is covered by artificial surfaces (76%) within 2 miles, artificial surfaces (49%) within 10 miles, and water (29%) and shrubs (26%) within 50 miles.

2 miles
709 ft
10 miles
2,549 ft
50 miles
6,450 ft
treesshrubsgrasslandartificial surfacesbare terrainwater
September weather nearby: Lemon Grove 1.9 mi · Spring Valley 1.9 mi · Casa de Oro-Mount Helix 3.1 mi · El Cajon 3.7 mi · La Presa 4.3 mi · Rancho San Diego 5.6 mi · Santee 5.6 mi · Bostonia 5.6 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 La Mesa (32.7678°, -117.0231°, elevation 528 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).