San Jose weather in September

In September, San Jose sees average daytime highs of 78°F and overnight lows near 56°F, with 0.1 in of rain across 0.5 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 10th-wettest month of the year here.

Day-to-day highs hold fairly steady near 78°F through the month. The sky is clear or mostly clear about 87% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 48 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 Jose's 3rd-clearest and 12th-windiest month. For the whole year in context, see San Jose's year-round climate.

Daytime high
78°
3rd warmest
Overnight low
56°
11th coldest
Rainfall
0.1 in
0.5 wet days
Daylight
12 h 12 min
5:55 AM – 6:09 PM
Cloud cover
14%
3rd clearest
Wind
4 mph
12th windiest
Solar energy
5.87 kWh/m²
Travel score
9.2
out of 10

San Jose is city and county seat of Santa Clara County, California, United States.

Density
2,140/km²
people per km²
Founded
1777

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 78°F through the month.

A typical September day in San Jose reaches about 78°F in the afternoon and slips back to 56°F overnight — a 22°F spread between the day's warmth and the night's chill. On most days the high lands between 69°F and 88°F. Set against its neighbours, September runs on par with August and about 5°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17957
27957
37957
47857
57857
67856
77856
87856
97856
107856
117856
127856
137856
147756
157756
167756
177756
187756
197756
207756
217756
227756
237755
247755
257755
267755
277755
287655
297655
307655

San Jose weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan57° / 42°5.19.19.74.2
Feb59° / 44°5.39.310.64.6
Mar62° / 45°3.99.311.75.4
Apr65° / 47°1.85.612.96.7
May69° / 50°0.93.4147.8
Jun74° / 53°0.2114.59.1
Jul78° / 56°0.00.114.39.4
Aug78° / 56°0.00.213.49.2
Sep78° / 56°0.10.512.39.2
Oct73° / 52°1.23118.5
Nov63° / 46°2.46106.2
Dec57° / 42°4.79.29.54.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 87% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 5% 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 (%)
1955
2955
3955
4955
5946
6946
7946
8946
9946
10946
11946
12937
13937
14937
15937
16937
17928
18919
19919
20919
21919
229010
239010
249010
258911
268911
278911
288812
298812
308713

Chance of precipitation in September

Any precipitation

San Jose 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 (%)
10
20
31
41
51
61
71
81
91
101
111
121
131
142
152
162
172
182
192
202
212
223
233
243
253
263
274
284
294
304

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the dry band about 79% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
175241
275241
376231
476231
576231
676231
777221
877221
977221
1078211
1178211
1278211
1378211
1478211
1578211
1678211
1778211
1879201
1979201
2079201
2180191
2280191
2381181
2482180
2583170
2684160
2785150
2885150
2986140
3087130

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 48 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 66 minutes over September. Sunrise moves from 5:42 AM to 6:07 AM, and sunset from 6:33 PM to 5:47 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:426:33
212.85:436:31
312.85:446:29
412.75:456:28
512.75:456:26
612.65:466:25
712.65:476:23
812.65:486:22
912.55:496:20
1012.55:506:19
1112.45:516:17
1212.45:516:15
1312.45:526:14
1412.35:536:12
1512.35:546:11
1612.25:556:09
1712.25:566:07
1812.25:576:06
1912.15:576:04
2012.15:586:03
2112.05:596:01
2212.06:005:59
2311.96:015:58
2411.96:025:56
2511.96:035:55
2611.86:035:53
2711.86:045:51
2811.76:055:50
2911.76:065:48
3011.76:075:47

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.87 kWh/m².

For context, solar energy here swings from a low near 2.34 kWh/m² to a high of 7.85 kWh/m² in June across the year — September's 5.87 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.5Intense
26.5Intense
36.4Intense
46.4Intense
56.3Intense
66.3Intense
76.3Intense
86.2Intense
96.2Intense
106.1Intense
116.1Intense
126.0Intense
136.0Bright
145.9Bright
155.9Bright
165.8Bright
175.8Bright
185.7Bright
195.7Bright
205.7Bright
215.6Bright
225.6Bright
235.5Bright
245.5Bright
255.4Bright
265.4Bright
275.3Bright
285.3Bright
295.2Bright
305.2Bright
Planning a trip in September

Hazard calendar for San Jose

In seasonPeak

None of San Jose's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

San Jose's rainy season runs November–March, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit San Jose?

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

9.2
Sightseeing
2nd-best month of the year
8.3
Beach & pool
3rd-best month of the year

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

What to pack for San Jose in September

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

In September, San Jose sees daytime highs around 78°F and nights near 56°F. Worth packing: light clothes and sun protection.

light clothessun protection

Sea temperature near San Jose in September

The nearest coast averages about 59°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 59°F and coldest in April near 54°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

52°54°56°58°60°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°F)Comfort
Jan54Bracing
Feb54Bracing
Mar54Bracing
Apr54Bracing
May54Bracing
Jun55Bracing
Jul57Bracing
Aug59Bracing
Sep59Bracing
Oct58Bracing
Nov56Bracing
Dec55Bracing

UV index in San Jose in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — 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 Jose peaks around June 23 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 15 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJun 23UV 10Dec 15UV 2
UV index (midday)Level
Jan3Moderate
Feb4Moderate
Mar5Moderate
Apr7High
May8Very high
Jun10Extreme
Jul10Extreme
Aug10Very high
Sep6High
Oct5High
Nov2Moderate
Dec2Moderate

Air quality in San Jose 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 Jose is worst in August — around 25 µg/m³ PM2.5 (moderate), about 2.5× the cleanest month (June, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateAug 1824 µg/m³Jun 1110 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb18Moderate
Mar16Moderate
Apr12Moderate
May10Good
Jun10Good
Jul11Good
Aug25Moderate
Sep17Moderate
Oct20Moderate
Nov18Moderate
Dec13Moderate
Location & terrain

Where is San Jose?

San Jose sits at 37.3°N, 121.9°W, 85 ft above sea level, in United States. The nearest listed city is Santa Clara, 3.7 mi away.

Topography around San Jose

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

Within 2 miles, the terrain around San Jose has only modest variations in elevation — a maximum elevation change of 115 ft around an average of 92 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,992 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,373 ft.

The land around San Jose is covered by artificial surfaces (79%) within 2 miles, artificial surfaces (54%), trees (20%) and grassland (20%) within 10 miles, and grassland (28%), water (28%) and trees (25%) within 50 miles.

2 miles
115 ft
10 miles
2,992 ft
50 miles
4,373 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Santa Clara 3.7 mi · Alum Rock 4.3 mi · Campbell 5.0 mi · Milpitas 6.2 mi · Cupertino 7.5 mi · Sunnyvale 8.1 mi · Saratoga 8.7 mi · Los Gatos 8.7 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 Jose (37.3394°, -121.895°, elevation 85 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).