San Luis weather in September

In September, San Luis sees average daytime highs of 101°F and overnight lows near 78°F, with 0.5 in of rain across 2.2 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 1st-wettest month of the year here.

Highs ease over the month, from about 104°F in the first days to 98°F by the end. The sky is clear or mostly clear about 87% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 42 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 Luis's 2nd-clearest and 12th-windiest month. For the whole year in context, see San Luis's year-round climate.

Daytime high
101°
4th warmest
Overnight low
78°
10th coldest
Rainfall
0.5 in
2.2 wet days
Daylight
12 h 12 min
6:28 AM – 6:39 PM
Cloud cover
16%
2nd clearest
Wind
5 mph
12th windiest
Solar energy
6.29 kWh/m²
Travel score
1.2
out of 10

San Luis is city in Yuma County, Arizona, United States.

Density
356/km²
people per km²
Founded
1930

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 104°F in the first days to 98°F by the end.

A typical September day in San Luis reaches about 101°F in the afternoon and slips back to 78°F overnight — a 23°F spread between the day's warmth and the night's chill. On most days the high lands between 94°F and 107°F. Set against its neighbours, September runs about 5°F cooler than August and about 10°F warmer than October.

60°80°100°151015202530
Avg high (°F)Avg low (°F)
110482
210482
310482
410382
510381
610381
710381
810380
910280
1010280
1110279
1210279
1310179
1410178
1510178
1610178
1710177
1810077
1910077
2010076
2110076
229976
239975
249975
259975
269874
279874
289873
299773
309773

How September really feels in San Luis

Once humidity and wind are folded in, September averages 30 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
30
11 feel dangerously hot (≥ 102°F)
Days feeling ≤ 32°F
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

San Luis weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan71° / 49°0.41.510.18.4
Feb74° / 52°0.52.310.88.6
Mar81° / 56°0.41.511.88.1
Apr87° / 61°0.10.612.86.1
May95° / 68°0.00.213.63.5
Jun103° / 75°0.00.214.10.7
Jul106° / 83°0.21.513.90.0
Aug106° / 84°0.42.913.20.0
Sep101° / 78°0.52.212.21.2
Oct91° / 67°0.20.911.24.9
Nov78° / 56°0.20.810.38.6
Dec69° / 48°0.41.79.98.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 87% 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 6%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1928
2928
3928
4928
5937
6937
7946
8946
9946
10946
11955
12955
13955
14955
15955
16946
17946
18955
19955
20955
21955
22946
23946
24946
25946
26937
27937
28937
29937
30937

Chance of precipitation in September

Any precipitation

San Luis gets around 0.5 in of rain over 2.2 wet days in September, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 7% and peaks near 12% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%151015202530
Rain chance (%)
112
212
312
412
512
611
711
811
910
1010
119
128
138
147
157
167
176
186
195
205
215
225
235
244
254
264
274
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 41% of days. Sticky, muggy-or-worse air turns up on roughly 30% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
11892030203
21991930203
320101929202
421101929192
523101828192
624101827182
726111826172
828111825171
930111724161
1032121723151
1134121722141
1236131720131
1338131719121
1440141718111
1542141617101
164315161691
174515161581
184715151571
194816151471
204916141460
215116141360
225316131350
235416131250
245417121250
255517121240
265716111140
275816111140
285916101140
296116101030
30621691030

Wind in September

Winds average 5 mph in September, the calmest month.

Across September, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 42 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 60 minutes over September. Sunrise moves from 6:18 AM to 6:37 AM, and sunset from 7:00 PM to 6:20 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.76:187:00
212.76:186:59
312.66:196:57
412.66:206:56
512.66:206:55
612.56:216:53
712.56:226:52
812.56:226:50
912.46:236:49
1012.46:246:48
1112.46:246:46
1212.36:256:45
1312.36:266:44
1412.36:266:42
1512.26:276:41
1612.26:286:39
1712.26:286:38
1812.16:296:37
1912.16:306:35
2012.16:306:34
2112.06:316:32
2212.06:316:31
2312.06:326:30
2411.96:336:28
2511.96:336:27
2611.96:346:25
2711.86:356:24
2811.86:366:23
2911.86:366:21
3011.76:376:20

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.29 kWh/m².

For context, solar energy here swings from a low near 3.4 kWh/m² to a high of 8.49 kWh/m² in June across the year — September's 6.29 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.6Intense
26.6Intense
36.6Intense
46.6Intense
56.5Intense
66.5Intense
76.5Intense
86.5Intense
96.5Intense
106.4Intense
116.4Intense
126.4Intense
136.4Intense
146.3Intense
156.3Intense
166.3Intense
176.3Intense
186.3Intense
196.2Intense
206.2Intense
216.2Intense
226.1Intense
236.1Intense
246.1Intense
256.0Intense
266.0Bright
276.0Bright
285.9Bright
295.9Bright
305.9Bright
Planning a trip in September

Is September a good time to visit San Luis?

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

1.2
Sightseeing
9th-best month of the year
4.5
Beach & pool
9th-best month of the year

September is a weaker month for outdoor sightseeing in San Luis.

What to pack for San Luis in September

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

In September, San Luis sees daytime highs around 101°F and nights near 78°F. Pack light clothes and sun protection.

light clothessun protection

UV index in San Luis in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 9 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Luis peaks around June 23 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 18 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateVery highExtremeVery highHighModerateJun 23UV 11Dec 18UV 3
UV index (midday)Level
Jan4Moderate
Feb5Moderate
Mar5Moderate
Apr8Very high
May8Very high
Jun11Extreme
Jul11Extreme
Aug10Very high
Sep9Very high
Oct6High
Nov4Moderate
Dec3Moderate
Location & terrain

Where is San Luis?

San Luis sits at 32.5°N, 114.8°W, 131 ft above sea level, in United States. The nearest listed city is San Luis Río Colorado, 2.5 mi away.

Topography around San Luis

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

Within 2 miles, the terrain around San Luis has only modest variations in elevation — a maximum elevation change of 89 ft around an average of 118 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 180 ft; within 50 miles, large variations in elevation — a maximum elevation change of 3,652 ft.

The land around San Luis is covered by artificial surfaces (46%), bare terrain (26%) and cropland (24%) within 2 miles, bare terrain (45%) and cropland (41%) within 10 miles, and bare terrain (73%) within 50 miles.

2 miles
89 ft
10 miles
180 ft
50 miles
3,652 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: San Luis Río Colorado 2.5 mi · Somerton 8.7 mi · Yuma 19 mi · Ciudad Guadalupe Victoria 23 mi · Fortuna Foothills 25 mi · Puebla 34 mi · Mexicali 40 mi · Calexico 43 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 Luis (32.487°, -114.7822°, elevation 131 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. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).