Lafayette weather in September

In September, Lafayette sees average daytime highs of 81°F and overnight lows near 56°F, with 0.1 in of rain across 0.4 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 81°F through the month. The sky is clear or mostly clear about 86% 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 Lafayette's 3rd-clearest and 6th-windiest month. For the whole year in context, see Lafayette's year-round climate.

Daytime high
81°
3rd warmest
Overnight low
56°
10th coldest
Rainfall
0.1 in
0.4 wet days
Daylight
12 h 12 min
5:56 AM – 6:10 PM
Cloud cover
14%
3rd clearest
Wind
6 mph
6th windiest
Solar energy
5.96 kWh/m²
Travel score
8.7
out of 10

Lafayette is city in Contra Costa County, California, United States.

Density
648/km²
people per km²
Founded
1848

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 81°F through the month.

A typical September day in Lafayette reaches about 81°F in the afternoon and slips back to 56°F overnight — a 25°F spread between the day's warmth and the night's chill. On most days the high lands between 73°F and 91°F. Set against its neighbours, September runs on par with August and about 6°F warmer than October.

50°60°70°80°90°151015202530
Avg high (°F)Avg low (°F)
18357
28357
38257
48257
58257
68257
78257
88257
98257
108256
118256
128156
138156
148156
158156
168156
178156
188156
198156
208156
218156
228156
238156
248055
258055
268055
278055
288055
298055
307955

Lafayette 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°3.78.99.74.2
Feb61° / 44°3.78.710.55.1
Mar65° / 47°2.88.311.76.3
Apr69° / 49°1.34.7137.4
May74° / 52°0.72.9148.5
Jun80° / 55°0.10.814.68.8
Jul82° / 57°0.00.214.48.8
Aug82° / 57°0.10.213.58.7
Sep81° / 56°0.10.412.38.7
Oct75° / 53°0.82.8118.6
Nov65° / 47°1.75.4106.5
Dec57° / 43°3.38.69.44.3

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 86% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 7% of September, with mostly cloudy or overcast conditions the remaining 7%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1964
2964
3964
4964
5964
6964
7964
8964
9964
10955
11955
12955
13955
14946
15946
16937
17937
18937
19928
20928
21928
229010
239010
249010
259010
268911
278812
288812
298713
308713

Chance of precipitation in September

Any precipitation

Lafayette 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
283
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 67% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
156404
258384
359374
460364
561354
662344
763334
864324
965314
1065314
1167303
1267303
1366313
1466313
1567312
1667312
1767312
1867312
1968311
2068311
2168311
2269301
2369301
2470291
2571281
2671281
2772271
2874251
2975241
3076231

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
157calm
167calm
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 5:42 AM to 6:08 AM, and sunset from 6:34 PM to 5:47 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:426:34
212.85:436:32
312.85:446:31
412.75:456:29
512.75:466:28
612.75:476:26
712.65:486:25
812.65:496:23
912.55:496:21
1012.55:506:20
1112.45:516:18
1212.45:526:16
1312.45:536:15
1412.35:546:13
1512.35:556:12
1612.25:566:10
1712.25:566:08
1812.25:576:07
1912.15:586:05
2012.15:596:04
2112.06:006:02
2212.06:016:00
2311.96:025:59
2411.96:035:57
2511.96:045:55
2611.86:045:54
2711.86:055:52
2811.76:065:51
2911.76:075:49
3011.76:085:47

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.96 kWh/m².

For context, solar energy here swings from a low near 2.14 kWh/m² to a high of 8.05 kWh/m² in June across the year — September's 5.96 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.7Intense
26.6Intense
36.6Intense
46.5Intense
56.5Intense
66.4Intense
76.4Intense
86.3Intense
96.3Intense
106.2Intense
116.2Intense
126.1Intense
136.1Intense
146.0Intense
156.0Bright
165.9Bright
175.9Bright
185.8Bright
195.8Bright
205.7Bright
215.7Bright
225.6Bright
235.5Bright
245.5Bright
255.4Bright
265.4Bright
275.3Bright
285.3Bright
295.2Bright
305.2Bright
Planning a trip in September

Is September a good time to visit Lafayette?

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

8.7
Sightseeing
3rd-best month of the year
8.9
Beach & pool
3rd-best month of the year

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

What to pack for Lafayette in September

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

In September, Lafayette sees daytime highs around 81°F and nights near 56°F. Pack light clothes. Worth having: sun protection.

light clothessun protection

Sea temperature near Lafayette 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 28 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 Lafayette 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 Lafayette peaks around June 23 at about 10 (very high) — 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 highHighModerateJun 23UV 10Dec 15UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar4Moderate
Apr6High
May8Very high
Jun10Very high
Jul10Very high
Aug10Very high
Sep6High
Oct5High
Nov2Moderate
Dec2Low

Air quality in Lafayette 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 Lafayette 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 Lafayette?

Lafayette sits at 37.9°N, 122.1°W, 308 ft above sea level, in United States. The nearest listed city is Walnut Creek, 3.1 mi away.

Topography around Lafayette

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

Within 2 miles, the terrain around Lafayette has significant variations in elevation — a maximum elevation change of 951 ft around an average of 535 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,028 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,452 ft.

The land around Lafayette is covered by trees (63%) and grassland (21%) within 2 miles, trees (47%), grassland (27%) and artificial surfaces (24%) within 10 miles, and grassland (28%), trees (23%) and water (23%) within 50 miles.

2 miles
951 ft
10 miles
3,028 ft
50 miles
4,452 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Walnut Creek 3.1 mi · Orinda 3.1 mi · Moraga 3.7 mi · Pleasant Hill 5.6 mi · Danville 8.1 mi · Concord 8.1 mi · Berkeley 8.7 mi · Martinez 9.3 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 Lafayette (37.8858°, -122.118°, elevation 308 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).