Castaic in Fall
In fall (September, October and November), Castaic sees average daytime highs around 76°F and overnight lows near 54°F, with 1.5 in of rain over about 6 wet days across the season. It is the 2nd-warmest season and the 3rd-wettest season.
Over the season highs ease from about 88°F in early September to 62°F by late November. The sky is clear or mostly clear about 74% of the time across fall, and the air most often feels dry.
Fall is Castaic's best season of the year to visit on our travel score. For the whole year in context, see Castaic's year-round climate.
- Avg daytime high
- 76°F
- 2nd-warmest season
- Avg overnight low
- 54°F
- Rainfall
- 1.5 in
- 6 wet days
- Avg wind
- 4 mph
- Travel score
- 7.8
- best season of the year
- Months
- Sep · Oct · Nov
Temperature in Castaic in Fall
Over the season highs ease from about 88°F in early September to 62°F by late November.
A typical fall day in Castaic reaches about 76°F and drops to 54°F overnight. The warmest of the three months is September, the coolest November.
Castaic 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 | 60° / 41° | 2.8 | 5.7 | 10 | 5.3 |
| Feb | 61° / 42° | 3.2 | 7 | 10.7 | 5.5 |
| Mar | 65° / 44° | 2.2 | 6 | 11.7 | 6.7 |
| Apr | 70° / 48° | 0.8 | 3.5 | 12.8 | 7.9 |
| May | 76° / 53° | 0.4 | 2.1 | 13.8 | 8.8 |
| Jun | 82° / 59° | 0.1 | 0.4 | 14.3 | 8.2 |
| Jul | 87° / 64° | 0.1 | 0.8 | 14.1 | 6.3 |
| Aug | 89° / 65° | 0.0 | 0.2 | 13.3 | 5.9 |
| Sep | 85° / 61° | 0.2 | 0.7 | 12.2 | 7.2 |
| Oct | 77° / 54° | 0.6 | 2.5 | 11.1 | 8.7 |
| Nov | 67° / 46° | 0.7 | 3 | 10.2 | 7.6 |
| Dec | 59° / 40° | 2.0 | 5.2 | 9.7 | 5.3 |
Cloud cover in Fall
The sky is clear or mostly clear about 74% of the time across fall.
Chance of precipitation in Fall
Castaic gets around 1.5 in of rain over 6 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 54 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 4.9 kWh/m².
Is fall a good time to visit Castaic?
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 Castaic for general sightseeing. The water and warmth also suit a beach or pool day.
What to pack for Castaic in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Castaic sees daytime highs around 76°F and nights near 54°F. Pack light clothes and sun protection. Worth having: a warm layer. About 6 days see rain.
Sea temperature near Castaic in Fall
The nearest coast averages about 65°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 38 mi away) is warmest in August at about 67°F and coldest in March near 58°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) | 58 | 58 | 58 | 58 | 60 | 63 | 66 | 67 | 67 | 65 | 62 | 60 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Cool | Cool | Cool | Cool | Cool | Cool | Cool | Cool |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 58 | Bracing |
| Feb | 58 | Bracing |
| Mar | 58 | Bracing |
| Apr | 58 | Bracing |
| May | 60 | Cool |
| Jun | 63 | Cool |
| Jul | 66 | Cool |
| Aug | 67 | Cool |
| Sep | 67 | Cool |
| Oct | 65 | Cool |
| Nov | 62 | Cool |
| Dec | 60 | Cool |
UV index in Castaic in Fall
Clear-sky midday UV across fall averages 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 Castaic peaks around June 23 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 15 at about 3 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 4 | 5 | 5 | 8 | 8 | 11 | 11 | 11 | 8 | 6 | 3 | 3 |
| Level | Moderate | Moderate | Moderate | Very high | Very high | Extreme | Extreme | Extreme | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 4 | Moderate |
| Feb | 5 | Moderate |
| Mar | 5 | Moderate |
| Apr | 8 | Very high |
| May | 8 | Very high |
| Jun | 11 | Extreme |
| Jul | 11 | Extreme |
| Aug | 11 | Extreme |
| Sep | 8 | Very high |
| Oct | 6 | High |
| Nov | 3 | Moderate |
| Dec | 3 | Moderate |
Air quality in Castaic 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 Castaic is worst in December — around 29 µg/m³ PM2.5 (moderate), about 2.4× the cleanest month (May, 12 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) | 18 | 17 | 17 | 15 | 12 | 14 | 25 | 26 | 24 | 18 | 23 | 29 |
| Level | Moderate | Moderate | Moderate | Moderate | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 18 | Moderate |
| Feb | 17 | Moderate |
| Mar | 17 | Moderate |
| Apr | 15 | Moderate |
| May | 12 | Good |
| Jun | 14 | Moderate |
| Jul | 25 | Moderate |
| Aug | 26 | Moderate |
| Sep | 24 | Moderate |
| Oct | 18 | Moderate |
| Nov | 23 | Moderate |
| Dec | 29 | Moderate |
Where is Castaic?
Castaic sits at 34.5°N, 118.6°W, 1,227 ft above sea level, in United States. The nearest listed city is Valencia, 3.1 mi away.
Topography around Castaic
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Castaic.
Within 2 miles, the terrain around Castaic has significant variations in elevation — a maximum elevation change of 1,043 ft around an average of 1,401 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,425 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,318 ft.
The land around Castaic is covered by grassland (41%) and shrubs (26%) within 2 miles, shrubs (35%) and grassland (35%) within 10 miles, and grassland (35%) 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 Castaic (34.4889°, -118.6229°, elevation 1,227 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.