San Rafael weather in September

In September, San Rafael sees average daytime highs of 73°F and overnight lows near 55°F, with 0.1 in of rain across 0.4 wet days and about 12.3 hours of daylight. It is the 1st-warmest and 10th-wettest month of the year here.

Day-to-day highs hold fairly steady near 73°F through the month. The sky is clear or mostly clear about 81% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 54 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 Rafael's 1st-clearest and 9th-windiest month. For the whole year in context, see San Rafael's year-round climate.

Daytime high
73°
1st warmest
Overnight low
55°
11th coldest
Rainfall
0.1 in
0.4 wet days
Daylight
12 h 12 min
5:57 AM – 6:12 PM
Cloud cover
23%
1st clearest
Wind
6 mph
9th windiest
Solar energy
5.77 kWh/m²
Travel score
9.0
out of 10

San Rafael is city and the county seat of Marin County, California, United States.

Density
1,019/km²
people per km²
Founded
1874

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 73°F through the month.

A typical September day in San Rafael reaches about 73°F in the afternoon and slips back to 55°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 66°F and 81°F. Set against its neighbours, September runs on par with August and about 3°F warmer than October.

50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
17356
27356
37356
47356
57356
67356
77356
87356
97356
107356
117356
127356
137355
147355
157355
167355
177355
187355
197355
207355
217355
227355
237355
247355
257355
267355
277355
287255
297255
307255

San Rafael weather by month

How September compares with the rest of the year at a glance. September is the 1st-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan56° / 44°4.59.99.73.9
Feb58° / 46°4.7910.54.4
Mar61° / 48°3.48.811.75.2
Apr63° / 49°1.54.9136.5
May67° / 52°0.83147.6
Jun71° / 54°0.20.814.68.6
Jul72° / 55°0.00.114.48.9
Aug73° / 56°0.00.213.59.0
Sep73° / 55°0.10.412.39.0
Oct70° / 53°1.02.9118.1
Nov62° / 48°2.269.95.9
Dec56° / 44°4.49.89.43.9

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 81% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 9% of September, with mostly cloudy or overcast conditions the remaining 9%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1955
2955
3955
4946
5946
6946
7946
8946
9937
10937
11937
12937
13928
14919
15919
16919
17919
18919
19919
208911
218911
228911
238812
248812
258713
268713
278713
288614
298614
308614

Chance of precipitation in September

Any precipitation

San Rafael gets around 0.1 in of rain over 0.4 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
81
91
101
111
121
131
141
151
162
172
182
192
202
212
222
232
242
253
263
273
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 76% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
170282
271272
372262
473252
573252
674242
774242
874242
975232
1075232
1175232
1275232
1376222
1476222
1576222
1676222
1776222
1877221
1977221
2077221
2177221
2277221
2378211
2478211
2579201
2680191
2780191
2881181
2982171
3083161

Wind in September

Winds average 6 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
286calm
296calm
306calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 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 72 minutes over September. Sunrise moves from 5:44 AM to 6:10 AM, and sunset from 6:36 PM to 5:49 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:446:36
212.85:456:34
312.85:466:33
412.75:476:31
512.75:486:29
612.75:486:28
712.65:496:26
812.65:506:25
912.55:516:23
1012.55:526:21
1112.45:536:20
1212.45:546:18
1312.45:556:17
1412.35:556:15
1512.35:566:13
1612.25:576:12
1712.25:586:10
1812.25:596:08
1912.16:006:07
2012.16:016:05
2112.06:026:04
2212.06:036:02
2311.96:036:00
2411.96:045:59
2511.96:055:57
2611.86:065:55
2711.86:075:54
2811.76:085:52
2911.76:095:51
3011.76:105:49

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.77 kWh/m².

For context, solar energy here swings from a low near 2.13 kWh/m² to a high of 7.85 kWh/m² in June across the year — September's 5.77 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.4Intense
26.4Intense
36.3Intense
46.3Intense
56.3Intense
66.2Intense
76.2Intense
86.1Intense
96.1Intense
106.0Intense
116.0Bright
125.9Bright
135.9Bright
145.8Bright
155.8Bright
165.7Bright
175.7Bright
185.6Bright
195.6Bright
205.5Bright
215.5Bright
225.4Bright
235.4Bright
245.3Bright
255.3Bright
265.2Bright
275.2Bright
285.1Bright
295.1Bright
305.0Bright
Planning a trip in September

Hazard calendar for San Rafael

In seasonPeak

None of San Rafael'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 Rafael'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 Rafael?

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

9.0
Sightseeing
1st-best month of the year
6.7
Beach & pool
1st-best month of the year

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

What to pack for San Rafael in September

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

In September, San Rafael sees daytime highs around 73°F and nights near 55°F. Worth packing: light clothes and sun protection.

light clothessun protection

Sea temperature near San Rafael in September

The nearest coast averages about 58°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 9 mi away) is warmest in September at about 58°F and coldest in April near 53°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
Jan53Bracing
Feb53Bracing
Mar54Bracing
Apr53Bracing
May53Bracing
Jun54Bracing
Jul56Bracing
Aug58Bracing
Sep58Bracing
Oct57Bracing
Nov55Bracing
Dec54Bracing

UV index in San Rafael 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 Rafael peaks around July 11 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 highHighModerateJul 11UV 10Dec 15UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar5Moderate
Apr6High
May8Very high
Jun10Extreme
Jul10Extreme
Aug10Very high
Sep6High
Oct5High
Nov2Moderate
Dec2Low

Air quality in San Rafael 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 Rafael is worst in September — around 29 µg/m³ PM2.5 (moderate), about 4.2× the cleanest month (June, 7 µg/m³).

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

010203040JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateSep 1829 µg/m³Jun 127 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb13Moderate
Mar13Moderate
Apr10Good
May8Good
Jun7Good
Jul10Good
Aug25Moderate
Sep29Moderate
Oct27Moderate
Nov16Moderate
Dec12Good
Location & terrain

Where is San Rafael?

San Rafael sits at 38.0°N, 122.5°W, 43 ft above sea level, in United States. The nearest listed city is Novato, 9.3 mi away.

Topography around San Rafael

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

Within 2 miles, the terrain around San Rafael has significant variations in elevation — a maximum elevation change of 994 ft around an average of 174 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,808 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,459 ft.

The land around San Rafael is covered by trees (62%) and artificial surfaces (31%) within 2 miles, trees (42%) and water (36%) within 10 miles, and water (40%), trees (23%) and grassland (22%) within 50 miles.

2 miles
994 ft
10 miles
2,808 ft
50 miles
4,459 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Novato 9.3 mi · San Pablo 9.9 mi · Richmond 11 mi · El Cerrito 12 mi · Pinole 13 mi · Hercules 14 mi · Chinatown 14 mi · Albany 14 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 Rafael (37.9735°, -122.5311°, elevation 43 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).