Alum Rock in Fall
In fall (September, October and November), Alum Rock sees average daytime highs around 72°F and overnight lows near 50°F, with 3.0 in of rain over about 9 wet days across the season. It is the 2nd-warmest season and the 3rd-wettest season.
Over the season highs ease from about 82°F in early September to 59°F by late November. The sky is clear or mostly clear about 69% of the time across fall, and the air most often feels dry.
Fall is Alum Rock's 2nd-best season to visit on our travel score. For the whole year in context, see Alum Rock's year-round climate.
- Avg daytime high
- 72°F
- 2nd-warmest season
- Avg overnight low
- 50°F
- Rainfall
- 3.0 in
- 9 wet days
- Avg wind
- 4 mph
- Travel score
- 7.9
- 2nd-best season
- Months
- Sep · Oct · Nov
Temperature in Alum Rock in Fall
Over the season highs ease from about 82°F in early September to 59°F by late November.
A typical fall day in Alum Rock reaches about 72°F and drops to 50°F overnight. The warmest of the three months is September, the coolest November.
Alum Rock weather by month
How the three fall months (September, October and November) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 56° / 40° | 4.4 | 9.1 | 9.7 | 4.1 |
| Feb | 58° / 42° | 4.4 | 9.2 | 10.6 | 4.4 |
| Mar | 61° / 44° | 3.3 | 9.2 | 11.7 | 5.4 |
| Apr | 65° / 45° | 1.6 | 5.7 | 12.9 | 6.7 |
| May | 71° / 49° | 0.8 | 3.4 | 14 | 8.1 |
| Jun | 77° / 53° | 0.2 | 0.8 | 14.5 | 9.1 |
| Jul | 82° / 57° | 0.1 | 0.2 | 14.3 | 8.8 |
| Aug | 82° / 57° | 0.0 | 0.3 | 13.4 | 8.8 |
| Sep | 80° / 56° | 0.1 | 0.6 | 12.3 | 8.9 |
| Oct | 73° / 51° | 1.0 | 2.8 | 11 | 8.6 |
| Nov | 63° / 44° | 1.9 | 5.7 | 10 | 6.2 |
| Dec | 56° / 40° | 3.9 | 8.8 | 9.5 | 4.0 |
Cloud cover in Fall
The sky is clear or mostly clear about 69% of the time across fall.
Chance of precipitation in Fall
Alum Rock gets around 3.0 in of rain over 9 wet days across fall. The line is the day-by-day chance of measurable precipitation.
Humidity in Fall
Most of fall feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Fall
Winds average 4 mph across fall.
Sunrise & sunset in Fall
Daylight runs from about 12 h 48 min in early September to 9 h 36 min by late November. The lit band spans sunrise to sunset each day.
Solar energy in Fall
Average shortwave solar energy reaching the ground each day across fall, about 4.4 kWh/m².
Hazard calendar for Alum Rock
None of Alum Rock's seasonal hazards peak in fall. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do.
Alum Rock's rainy season runs December–March, when most of the year's rain falls.
Is fall a good time to visit Alum Rock?
Our two travel scores rate fall for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
fall is one of the better times to visit Alum Rock for general sightseeing.
What to pack for Alum Rock in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Alum Rock sees daytime highs around 72°F and nights near 50°F. Worth packing: light clothes, a warm layer and sun protection. About 9 days see rain.
Sea temperature near Alum Rock in Fall
The nearest coast averages about 58°F across fall — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 30 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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 54 | 54 | 54 | 54 | 54 | 55 | 57 | 59 | 59 | 58 | 56 | 55 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 54 | Bracing |
| Feb | 54 | Bracing |
| Mar | 54 | Bracing |
| Apr | 54 | Bracing |
| May | 54 | Bracing |
| Jun | 55 | Bracing |
| Jul | 57 | Bracing |
| Aug | 59 | Bracing |
| Sep | 59 | Bracing |
| Oct | 58 | Bracing |
| Nov | 56 | Bracing |
| Dec | 55 | Bracing |
UV index in Alum Rock in Fall
Clear-sky midday UV across fall averages around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Alum Rock 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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 3 | 4 | 5 | 7 | 8 | 10 | 10 | 10 | 6 | 5 | 2 | 2 |
| Level | Moderate | Moderate | Moderate | High | Very high | Extreme | Extreme | Very high | High | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 3 | Moderate |
| Feb | 4 | Moderate |
| Mar | 5 | Moderate |
| Apr | 7 | High |
| May | 8 | Very high |
| Jun | 10 | Extreme |
| Jul | 10 | Extreme |
| Aug | 10 | Very high |
| Sep | 6 | High |
| Oct | 5 | High |
| Nov | 2 | Moderate |
| Dec | 2 | Moderate |
Air quality in Alum Rock in Fall
Average fine-particle pollution (PM2.5) through the year — so you can see where fall falls, not just the annual average.
Air quality in Alum Rock is worst in August — around 34 µg/m³ PM2.5 (moderate), about 4.9× the cleanest month (June, 7 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 13 | 13 | 13 | 10 | 8 | 7 | 9 | 34 | 16 | 14 | 15 | 12 |
| Level | Moderate | Moderate | Moderate | Good | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 13 | Moderate |
| Feb | 13 | Moderate |
| Mar | 13 | Moderate |
| Apr | 10 | Good |
| May | 8 | Good |
| Jun | 7 | Good |
| Jul | 9 | Good |
| Aug | 34 | Moderate |
| Sep | 16 | Moderate |
| Oct | 14 | Moderate |
| Nov | 15 | Moderate |
| Dec | 12 | Good |
Where is Alum Rock?
Alum Rock sits at 37.4°N, 121.8°W, 151 ft above sea level, in United States. The nearest listed city is San Jose, 4.3 mi away.
Topography around Alum Rock
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Alum Rock.
Within 2 miles, the terrain around Alum Rock has significant variations in elevation — a maximum elevation change of 1,129 ft around an average of 240 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,921 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,373 ft.
The land around Alum Rock is covered by artificial surfaces (73%) within 2 miles, artificial surfaces (42%), grassland (33%) and trees (22%) within 10 miles, and grassland (29%), trees (25%) and water (25%) within 50 miles.
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
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 Alum Rock (37.3661°, -121.8272°, elevation 151 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.