Rosemont weather in September

In September, Rosemont sees average daytime highs of 87°F and overnight lows near 59°F, with 0.1 in of rain across 0.7 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 90°F in the first days to 84°F by the end. 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 36 min by month's end. Set against the rest of the year, September is Rosemont's 3rd-clearest and 11th-windiest month. For the whole year in context, see Rosemont's year-round climate.

Daytime high
87°
4th warmest
Overnight low
59°
9th coldest
Rainfall
0.1 in
0.7 wet days
Daylight
12 h 12 min
5:52 AM – 6:07 PM
Cloud cover
14%
3rd clearest
Wind
4 mph
11th windiest
Solar energy
6 kWh/m²
Travel score
6.4
out of 10

Rosemont is census-designated place in Sacramento County, California, United States.

Density
2,014/km²
people per km²

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 90°F in the first days to 84°F by the end.

A typical September day in Rosemont reaches about 87°F in the afternoon and slips back to 59°F overnight — a 28°F spread between the day's warmth and the night's chill. On most days the high lands between 78°F and 96°F. Set against its neighbours, September runs about 4°F cooler than August and about 9°F warmer than October.

60°80°100°151015202530
Avg high (°F)Avg low (°F)
19061
29061
39060
48960
58960
68960
78960
88960
98860
108859
118859
128859
138759
148759
158759
168758
178758
188758
198658
208658
218658
228658
238558
248557
258557
268557
278557
288457
298456
308356

How September really feels in Rosemont

Once humidity and wind are folded in, September averages 3 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
3
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.

Rosemont 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
Jan57° / 41°4.99.59.64.2
Feb62° / 43°4.79.610.55.2
Mar66° / 46°4.19.211.76.3
Apr72° / 50°1.95.8137.5
May80° / 55°1.1414.17.7
Jun88° / 59°0.2114.65.9
Jul91° / 62°0.00.114.44.8
Aug91° / 61°0.10.213.55.0
Sep87° / 59°0.10.712.36.4
Oct78° / 53°1.43.2118.3
Nov65° / 45°2.66.69.96.5
Dec57° / 40°4.89.79.44.1

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
6955
7946
8946
9946
10946
11946
12937
13937
14937
15937
16937
17928
18928
19919
20919
21919
22919
239010
249010
259010
269010
278911
288911
299010
309010

Chance of precipitation in September

Any precipitation

Rosemont gets around 0.1 in of rain over 0.7 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 3% and peaks near 6% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
11
21
31
41
51
62
72
82
92
102
112
122
132
143
153
163
173
183
193
203
213
223
233
244
254
264
275
285
295
306

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 82% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
172244
273234
375223
475223
576213
677203
778193
878193
979183
1080182
1181172
1281172
1381172
1482171
1582171
1682171
1782171
1882171
1984160
2084160
2185150
2285150
2386140
2486140
2587130
2687130
2787130
2888120
2988120
3089110

Wind in September

Winds average 4 mph in September.

Across September, daily wind ranges from about 4 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 78 minutes over September. Sunrise moves from 5:39 AM to 6:05 AM, and sunset from 6:32 PM to 5:44 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:396:32
212.85:406:30
312.85:416:28
412.85:426:27
512.75:426:25
612.75:436:24
712.65:446:22
812.65:456:20
912.55:466:19
1012.55:476:17
1112.55:486:15
1212.45:496:14
1312.45:506:12
1412.35:516:10
1512.35:516:09
1612.25:526:07
1712.25:536:06
1812.25:546:04
1912.15:556:02
2012.15:566:01
2112.05:575:59
2212.05:585:57
2311.95:595:56
2411.96:005:54
2511.96:015:52
2611.86:025:51
2711.86:035:49
2811.76:035:47
2911.76:045:46
3011.66:055:44

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6 kWh/m².

For context, solar energy here swings from a low near 2.1 kWh/m² to a high of 8.21 kWh/m² in July across the year — September's 6 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.8Intense
26.7Intense
36.7Intense
46.6Intense
56.6Intense
66.5Intense
76.5Intense
86.4Intense
96.3Intense
106.3Intense
116.2Intense
126.2Intense
136.1Intense
146.1Intense
156.0Intense
166.0Bright
175.9Bright
185.9Bright
195.8Bright
205.8Bright
215.7Bright
225.6Bright
235.6Bright
245.5Bright
255.5Bright
265.4Bright
275.4Bright
285.3Bright
295.3Bright
305.2Bright
Planning a trip in September

Hazard calendar for Rosemont

In seasonPeak

None of Rosemont's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Rosemont'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 Rosemont?

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

6.4
Sightseeing
5th-best month of the year
8.9
Beach & pool
1st-best month of the year

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

What to pack for Rosemont in September

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

In September, Rosemont sees daytime highs around 87°F and nights near 59°F. Pack light clothes and sun protection.

light clothessun protection

UV index in Rosemont 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 Rosemont peaks around June 21 at about 10 (very high) — 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 highHighModerateJun 21UV 10Dec 14UV 2
UV index (midday)Level
Jan2Moderate
Feb3Moderate
Mar4Moderate
Apr6High
May8Very high
Jun10Very high
Jul10Very high
Aug9Very high
Sep6High
Oct5Moderate
Nov2Moderate
Dec2Low

Air quality in Rosemont 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 Rosemont is worst in August — around 27 µg/m³ PM2.5 (moderate), about 3.6× the cleanest month (June, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateAug 2126 µg/m³Jun 138 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb14Moderate
Mar15Moderate
Apr12Good
May9Good
Jun8Good
Jul11Good
Aug27Moderate
Sep23Moderate
Oct17Moderate
Nov19Moderate
Dec14Moderate
Location & terrain

Where is Rosemont?

Rosemont sits at 38.6°N, 121.4°W, 49 ft above sea level, in United States. The nearest listed city is Arden-Arcade, 3.7 mi away.

Topography around Rosemont

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

Within 2 miles, the terrain around Rosemont has only modest variations in elevation — a maximum elevation change of 108 ft around an average of 52 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 328 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 5,384 ft.

The land around Rosemont is covered by artificial surfaces (51%) and trees (20%) within 2 miles, artificial surfaces (43%), grassland (28%) and trees (20%) within 10 miles, and trees (34%), grassland (31%) and cropland (23%) within 50 miles.

2 miles
108 ft
10 miles
328 ft
50 miles
5,384 ft
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: Arden-Arcade 3.7 mi · Rancho Cordova 4.3 mi · Florin 4.3 mi · Carmichael 5.0 mi · Vineyard 6.2 mi · Sacramento 7.5 mi · Fair Oaks 8.1 mi · Foothill Farms 8.7 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 Rosemont (38.5519°, -121.3647°, elevation 49 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).