Alum Rock in Spring
In spring (March, April and May), Alum Rock sees average daytime highs around 66°F and overnight lows near 46°F, with 5.7 in of rain over about 18 wet days across the season. It is the 3rd-warmest season and the 2nd-wettest season.
Over the season highs climb from about 60°F in early March to 73°F by late May. The sky is clear or mostly clear about 47% of the time across spring, and the air most often feels dry.
Spring is Alum Rock's 3rd-best season to visit on our travel score. For the whole year in context, see Alum Rock's year-round climate.
- Avg daytime high
- 66°F
- 3rd-warmest season
- Avg overnight low
- 46°F
- Rainfall
- 5.7 in
- 18 wet days
- Avg wind
- 5 mph
- Travel score
- 6.7
- 3rd-best season
- Months
- Mar · Apr · May
Temperature in Alum Rock in Spring
Over the season highs climb from about 60°F in early March to 73°F by late May.
A typical spring day in Alum Rock reaches about 66°F and drops to 46°F overnight. The warmest of the three months is May, the coolest March.
Alum Rock weather by month
How the three spring months (March, April and May) 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 Spring
The sky is clear or mostly clear about 47% of the time across spring.
Chance of precipitation in Spring
Alum Rock gets around 5.7 in of rain over 18 wet days across spring. The line is the day-by-day chance of measurable precipitation.
Humidity in Spring
Most of spring feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Spring
Winds average 5 mph across spring.
Sunrise & sunset in Spring
Daylight runs from about 11 h 06 min in early March to 14 h 24 min by late May. The lit band spans sunrise to sunset each day.
Solar energy in Spring
Average shortwave solar energy reaching the ground each day across spring, about 6.1 kWh/m².
Hazard calendar for Alum Rock
In spring, Alum Rock overlaps its rainy season season. The full year is below, with each hazard's peak months called out.
Alum Rock's rainy season runs December–March, when most of the year's rain falls.
Is spring a good time to visit Alum Rock?
Our two travel scores rate spring for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
spring is a reasonable time to visit Alum Rock for sightseeing.
What to pack for Alum Rock in Spring
From spring's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In spring, Alum Rock sees daytime highs around 66°F and nights near 46°F. Pack sun protection. Worth having: a warm layer and rain gear. About 18 days see rain.
Sea temperature near Alum Rock in Spring
The nearest coast averages about 54°F across spring — 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 Spring
Clear-sky midday UV across spring averages around 7 — 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 Spring
Average fine-particle pollution (PM2.5) through the year — so you can see where spring 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.