Atwater weather in September

In September, Atwater sees average daytime highs of 90°F and overnight lows near 63°F, with 0.1 in of rain across 0.4 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 10th-wettest month of the year here.

Highs ease over the month, from about 93°F in the first days to 86°F by the end. The sky is clear or mostly clear about 89% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 48 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Atwater's 3rd-clearest and 6th-windiest month. For the whole year in context, see Atwater's year-round climate.

Daytime high
90°
4th warmest
Overnight low
63°
9th coldest
Rainfall
0.1 in
0.4 wet days
Daylight
12 h 12 min
5:50 AM – 6:04 PM
Cloud cover
12%
3rd clearest
Wind
5 mph
6th windiest
Solar energy
6.16 kWh/m²
Travel score
5.4
out of 10

Atwater is city in Merced County, California, United States.

Density
1,852/km²
people per km²
Founded
1922

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 93°F in the first days to 86°F by the end.

A typical September day in Atwater reaches about 90°F in the afternoon and slips back to 63°F overnight — a 27°F spread between the day's warmth and the night's chill. On most days the high lands between 81°F and 98°F. Set against its neighbours, September runs about 6°F cooler than August and about 10°F warmer than October.

60°80°100°151015202530
Avg high (°F)Avg low (°F)
19466
29366
39365
49365
59365
69265
79265
89264
99264
109164
119164
129163
139063
149063
159063
168962
178962
188962
198962
208962
218861
228861
238861
248761
258761
268760
278660
288660
298660
308559

How September really feels in Atwater

Once humidity and wind are folded in, September averages 15 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
15
heat index over the day's high
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.

Atwater weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan58° / 42°3.58.19.74.7
Feb63° / 44°3.18.410.65.7
Mar68° / 48°2.87.711.76.8
Apr75° / 52°1.24.712.97.9
May83° / 58°0.72.8147.1
Jun92° / 64°0.10.614.54.6
Jul97° / 68°0.00.214.32.8
Aug95° / 67°0.00.113.43.3
Sep90° / 63°0.10.412.35.4
Oct79° / 55°0.82.3118.3
Nov67° / 46°1.54.8107.1
Dec58° / 41°3.07.49.54.7

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 89% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 5% 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
4955
5955
6955
7955
8955
9955
10955
11955
12946
13946
14946
15946
16946
17946
18946
19937
20937
21928
22928
23928
24919
25919
26919
27919
28919
299010
309010

Chance of precipitation in September

Any precipitation

Atwater 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 3% 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
161
171
181
192
202
212
222
232
242
252
262
273
283
293
303

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 87% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
1831331
2841231
3841231
4851131
5851131
6851131
7861121
8871021
9871021
10871021
11871021
12881020
13891010
14891010
15891010
16881110
17881110
18881110
19881110
20881110
21881110
22881110
23881110
24881110
25881110
26881110
27881110
28881110
29891010
30901000

Wind in September

Winds average 5 mph in September.

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
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
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 48 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 66 minutes over September. Sunrise moves from 5:37 AM to 6:02 AM, and sunset from 6:27 PM to 5:42 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.85:376:27
212.85:386:26
312.85:396:24
412.75:396:23
512.75:406:21
612.65:416:20
712.65:426:18
812.65:436:17
912.55:446:15
1012.55:456:13
1112.45:456:12
1212.45:466:10
1312.45:476:09
1412.35:486:07
1512.35:496:05
1612.25:506:04
1712.25:516:02
1812.25:516:01
1912.15:525:59
2012.15:535:57
2112.05:545:56
2212.05:555:54
2311.95:565:53
2411.95:575:51
2511.95:575:49
2611.85:585:48
2711.85:595:46
2811.76:005:45
2911.76:015:43
3011.76:025:42

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.16 kWh/m².

For context, solar energy here swings from a low near 2.4 kWh/m² to a high of 8.29 kWh/m² in June across the year — September's 6.16 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.9Intense
26.8Intense
36.8Intense
46.7Intense
56.7Intense
66.6Intense
76.6Intense
86.5Intense
96.5Intense
106.5Intense
116.4Intense
126.3Intense
136.3Intense
146.3Intense
156.2Intense
166.2Intense
176.1Intense
186.0Intense
196.0Bright
205.9Bright
215.9Bright
225.8Bright
235.8Bright
245.7Bright
255.7Bright
265.6Bright
275.6Bright
285.5Bright
295.5Bright
305.4Bright
Planning a trip in September

Is September a good time to visit Atwater?

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

5.4
Sightseeing
7th-best month of the year
8.6
Beach & pool
1st-best month of the year

September is a reasonable time to visit Atwater for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Atwater in September

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

In September, Atwater sees daytime highs around 90°F and nights near 63°F. Pack light clothes and sun protection.

light clothessun protection

UV index in Atwater in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks 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 Atwater peaks around June 19 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 14 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 highVery highHighModerateJun 19UV 10Dec 14UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar4Moderate
Apr7High
May8Very high
Jun10Extreme
Jul10Very high
Aug10Very high
Sep7High
Oct5High
Nov2Moderate
Dec2Moderate

Air quality in Atwater 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 Atwater is worst in August — around 29 µg/m³ PM2.5 (moderate), about 3.6× the cleanest month (June, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateAug 1928 µg/m³Jun 118 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb14Moderate
Mar14Moderate
Apr11Good
May9Good
Jun8Good
Jul15Moderate
Aug29Moderate
Sep22Moderate
Oct17Moderate
Nov15Moderate
Dec12Moderate
Location & terrain

Where is Atwater?

Atwater sits at 37.3°N, 120.6°W, 151 ft above sea level, in United States. The nearest listed city is Merced, 7.5 mi away.

Topography around Atwater

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

Within 2 miles, the terrain around Atwater has only modest variations in elevation — a maximum elevation change of 56 ft around an average of 154 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 341 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 6,919 ft.

The land around Atwater is covered by artificial surfaces (39%), cropland (23%) and trees (22%) within 2 miles, cropland (32%), trees (29%) and grassland (28%) within 10 miles, and grassland (47%) and trees (30%) within 50 miles.

2 miles
56 ft
10 miles
341 ft
50 miles
6,919 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Merced 7.5 mi · Turlock 17 mi · Los Banos 24 mi · Chowchilla 25 mi · Ceres 25 mi · Modesto 29 mi · Patterson 30 mi · Oakdale 32 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 Atwater (37.3477°, -120.6091°, 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. 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).