South San Jose Hills weather in September

In September, South San Jose Hills sees average daytime highs of 85°F and overnight lows near 63°F, with 0.1 in of rain across 0.5 wet days and about 12.2 hours of daylight. It is the 3rd-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 87°F in the first days to 83°F by the end. The sky is clear or mostly clear about 86% 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 South San Jose Hills's 2nd-clearest and 12th-windiest month. For the whole year in context, see South San Jose Hills's year-round climate.

Daytime high
85°
3rd warmest
Overnight low
63°
10th coldest
Rainfall
0.1 in
0.5 wet days
Daylight
12 h 12 min
5:40 AM – 5:52 PM
Cloud cover
16%
2nd clearest
Wind
3 mph
12th windiest
Solar energy
6.19 kWh/m²
Travel score
7.2
out of 10

South San Jose Hills is census-designated place in Los Angeles County, California, United States.

Density
5,262/km²
people per km²

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 87°F in the first days to 83°F by the end.

A typical September day in South San Jose Hills reaches about 85°F in the afternoon and slips back to 63°F overnight — a 21°F spread between the day's warmth and the night's chill. On most days the high lands between 76°F and 94°F. Set against its neighbours, September runs about 2°F cooler than August and about 6°F warmer than October.

60°80°100°151015202530
Avg high (°F)Avg low (°F)
18765
28765
38765
48765
58765
68665
78665
88664
98664
108564
118564
128564
138564
148563
158463
168463
178463
188463
198462
208462
218462
228462
238362
248362
258362
268362
278362
288361
298361
308261

South San Jose Hills weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan64° / 46°3.35.8106.7
Feb65° / 47°3.56.410.76.6
Mar67° / 49°2.25.911.77.0
Apr71° / 52°0.93.212.88.0
May75° / 56°0.42.113.78.7
Jun80° / 60°0.10.414.28.8
Jul85° / 64°0.10.4147.1
Aug87° / 65°0.00.113.36.5
Sep85° / 63°0.10.512.27.2
Oct79° / 58°0.62.111.18.6
Nov71° / 51°0.82.510.28.2
Dec64° / 46°2.259.86.8

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 86% 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
9937
10937
11937
12937
13946
14937
15937
16937
17937
18937
19928
20928
21928
22928
23928
24919
259010
269010
279010
289010
299010
309010

Chance of precipitation in September

Any precipitation

South San Jose Hills gets around 0.1 in of rain over 0.5 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 2% and peaks near 4% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
11
21
31
41
51
61
71
82
92
102
112
122
132
142
152
162
172
182
192
202
212
222
232
242
253
263
273
283
293
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 49% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
12250262
22350252
32449252
42549242
52549232
62649222
72750212
82850202
92950192
102952172
113052162
123152152
133253141
143353131
153453121
163552121
173652111
183751111
193851101
203950101
21405091
22414991
23424891
24444781
25454680
26474570
27484470
28504370
29534160
30544060

Wind in September

Winds average 3 mph in September, the calmest month.

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

0246810151015202530
Wind speed (mph)Feels
13calm
23calm
33calm
43calm
53calm
63calm
73calm
83calm
93calm
103calm
113calm
123calm
133calm
143calm
153calm
163calm
173calm
183calm
193calm
203calm
213calm
223calm
233calm
243calm
253calm
263calm
273calm
283calm
293calm
303calm

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 5:29 AM to 5:50 AM, and sunset from 6:14 PM to 5:32 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.75:296:14
212.75:306:12
312.75:306:11
412.65:316:09
512.65:326:08
612.65:336:07
712.55:336:05
812.55:346:04
912.55:356:02
1012.45:356:01
1112.45:365:59
1212.45:375:58
1312.35:385:57
1412.35:385:55
1512.25:395:54
1612.25:405:52
1712.25:405:51
1812.15:415:49
1912.15:425:48
2012.15:435:46
2112.05:435:45
2212.05:445:43
2312.05:455:42
2411.95:455:41
2511.95:465:39
2611.85:475:38
2711.85:485:36
2811.85:485:35
2911.75:495:33
3011.75:505:32

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.19 kWh/m².

For context, solar energy here swings from a low near 2.96 kWh/m² to a high of 8.03 kWh/m² in June across the year — September's 6.19 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.8Intense
26.8Intense
36.7Intense
46.7Intense
56.7Intense
66.6Intense
76.6Intense
86.5Intense
96.5Intense
106.4Intense
116.4Intense
126.4Intense
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
285.6Bright
295.6Bright
305.5Bright
Planning a trip in September

Is September a good time to visit South San Jose Hills?

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

7.2
Sightseeing
6th-best month of the year
9.2
Beach & pool
2nd-best month of the year

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

What to pack for South San Jose Hills in September

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

In September, South San Jose Hills sees daytime highs around 85°F and nights near 63°F. Pack light clothes and sun protection.

light clothessun protection

Sea temperature near South San Jose Hills 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 27 mi away) is warmest in August at about 69°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
Jan59Cool
Feb59Cool
Mar59Cool
Apr60Cool
May63Cool
Jun65Cool
Jul68Refreshing
Aug69Refreshing
Sep69Refreshing
Oct67Cool
Nov64Cool
Dec60Cool

UV index in South San Jose Hills 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 South San Jose Hills peaks around July 11 at about 11 (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 highHighModerateJul 11UV 11Dec 16UV 3
UV index (midday)Level
Jan4Moderate
Feb5Moderate
Mar5Moderate
Apr8Very high
May8Very high
Jun11Extreme
Jul11Extreme
Aug10Extreme
Sep8Very high
Oct6High
Nov3Moderate
Dec3Moderate

Air quality in South San Jose Hills 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 South San Jose Hills 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 South San Jose Hills?

South San Jose Hills sits at 34.0°N, 117.9°W, 417 ft above sea level, in United States. The nearest listed city is Walnut, 2.5 mi away.

Topography around South San Jose Hills

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

Within 2 miles, the terrain around South San Jose Hills has only modest variations in elevation — a maximum elevation change of 817 ft around an average of 522 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,926 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 10,013 ft.

The land around South San Jose Hills is covered by artificial surfaces (76%) within 2 miles, artificial surfaces (64%) within 10 miles, and artificial surfaces (26%) and water (21%) within 50 miles.

2 miles
817 ft
10 miles
1,926 ft
50 miles
10,013 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Walnut 2.5 mi · Rowland Heights 2.5 mi · La Puente 2.5 mi · Valinda 3.1 mi · Hacienda Heights 3.7 mi · West Covina 4.3 mi · West Puente Valley 4.3 mi · Avocado Heights 5.0 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 South San Jose Hills (34.0128°, -117.9048°, elevation 417 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).