Mason weather in September

In September, Mason sees average daytime highs of 78°F and overnight lows near 59°F, with 2.7 in of rain across 8 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 12th-wettest month of the year here.

Highs ease over the month, from about 82°F in the first days to 73°F by the end. The sky is clear or mostly clear about 42% 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 Mason's 1st-clearest and 10th-windiest month. For the whole year in context, see Mason's year-round climate.

Daytime high
78°
4th warmest
Overnight low
59°
9th coldest
Rainfall
2.7 in
8 wet days
Daylight
12 h 18 min
6:24 AM – 6:39 PM
Cloud cover
49%
1st clearest
Wind
6 mph
10th windiest
Solar energy
4.58 kWh/m²
Travel score
7.2
out of 10

Mason is city in Warren County, Ohio, United States.

Density
676/km²
people per km²
Founded
1815

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 82°F in the first days to 73°F by the end.

A typical September day in Mason reaches about 78°F in the afternoon and slips back to 59°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 68°F and 87°F. Set against its neighbours, September runs about 6°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18264
28264
38264
48163
58163
68162
78062
88062
98061
108061
117961
127960
137960
147859
157859
167859
177758
187758
197657
207657
217657
227556
237556
247555
257455
267455
277454
287354
297353
307353

How September really feels in Mason

Once humidity and wind are folded in, September averages 0 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
0
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Mason weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 12th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan39° / 25°3.410.44.39.50.0
Feb42° / 27°3.09.43.810.50.4
Mar52° / 35°4.211.4211.72.7
Apr65° / 46°4.712.70.5135.3
May73° / 56°4.713.1014.16.2
Jun82° / 65°4.212.2014.75.8
Jul85° / 68°3.511.2014.55.3
Aug83° / 66°2.99.5013.55.9
Sep78° / 59°2.78012.37.2
Oct65° / 47°3.08.50.1116.1
Nov53° / 37°3.49.30.89.83.0
Dec43° / 30°3.810.42.99.30.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 42% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 41%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16040
26040
36040
46040
56040
66040
76040
86040
96040
105941
115941
125941
135842
145743
155743
165842
175842
185743
195743
205842
215842
225842
235842
246040
256040
266040
276040
286040
296040
306040

Chance of precipitation in September

Any precipitation

Mason gets around 2.7 in of rain over 8 wet days in September, the driest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 26% and peaks near 29% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
129
229
329
429
528
628
727
827
926
1026
1126
1225
1325
1426
1526
1626
1726
1826
1926
2026
2126
2226
2326
2426
2526
2626
2726
2825
2925
3024

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 40% of days. Sticky, muggy-or-worse air turns up on roughly 19% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11525202811
21626202710
31727202610
4192819259
5202819248
6222919247
7242918236
8262918225
9282918214
10292918204
11312918193
12332819183
13352719172
14362719162
15382619161
16402518151
17422418141
18452318131
19472218131
20492217120
21512117110
22542016100
23552015100
2457191590
2559181490
2661181380
2762171380
2865161270
2965161270
3066151270

Wind in September

Winds average 6 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
15calm
25calm
35calm
45calm
55calm
65calm
75calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
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 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 6:10 AM to 6:37 AM, and sunset from 7:04 PM to 6:16 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.96:107:04
212.96:117:02
312.86:127:01
412.86:136:59
512.76:146:58
612.76:156:56
712.66:156:54
812.66:166:53
912.66:176:51
1012.56:186:49
1112.56:196:48
1212.46:206:46
1312.46:216:44
1412.36:226:43
1512.36:236:41
1612.36:246:39
1712.26:256:37
1812.26:266:36
1912.16:276:34
2012.16:286:32
2112.06:296:31
2212.06:306:29
2311.96:316:27
2411.96:326:26
2511.96:336:24
2611.86:346:22
2711.86:356:21
2811.76:356:19
2911.76:366:17
3011.66:376:16

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.58 kWh/m².

For context, solar energy here swings from a low near 1.68 kWh/m² to a high of 6.18 kWh/m² in June across the year — September's 4.58 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.1Bright
25.1Bright
35.0Bright
45.0Bright
55.0Bright
64.9Bright
74.9Bright
84.9Bright
94.8Bright
104.8Bright
114.8Bright
124.7Bright
134.7Bright
144.7Bright
154.6Bright
164.6Bright
174.5Bright
184.5Bright
194.5Bright
204.4Bright
214.4Bright
224.3Bright
234.3Bright
244.2Bright
254.2Bright
264.2Bright
274.1Bright
284.1Bright
294.0Bright
304.0Bright
Planning a trip in September

Is September a good time to visit Mason?

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

7.2
Sightseeing
1st-best month of the year
6.5
Beach & pool
3rd-best month of the year

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

What to pack for Mason in September

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

In September, Mason sees daytime highs around 78°F and nights near 59°F. Worth packing: light clothes, rain gear and sun protection. About 8 days see rain.

light clothesrain gearsun protection

UV index in Mason 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 Mason peaks around June 21 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 21UV 9Dec 22UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov3Moderate
Dec2Low

Air quality in Mason 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 Mason is worst in July — around 19 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1418 µg/m³Oct 248 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb11Good
Mar11Good
Apr12Good
May15Moderate
Jun18Moderate
Jul19Moderate
Aug16Moderate
Sep13Moderate
Oct8Good
Nov9Good
Dec9Good
Location & terrain

Where is Mason?

Mason sits at 39.4°N, 84.3°W, 810 ft above sea level, in United States. The nearest listed city is Lebanon, 7.5 mi away.

Topography around Mason

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

Within 2 miles, the terrain around Mason has only modest variations in elevation — a maximum elevation change of 240 ft around an average of 817 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 492 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 912 ft.

The land around Mason is covered by grassland (39%), trees (36%) and artificial surfaces (22%) within 2 miles, trees (43%) and grassland (29%) within 10 miles, and trees (42%) and cropland (36%) within 50 miles.

2 miles
240 ft
10 miles
492 ft
50 miles
912 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Lebanon 7.5 mi · Forest Park 11 mi · Middletown 12 mi · Fairfield 14 mi · Hamilton 14 mi · Springboro 14 mi · Norwood 16 mi · White Oak 19 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 Mason (39.3601°, -84.3099°, elevation 810 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).