Denison weather in September

In September, Denison sees average daytime highs of 85°F and overnight lows near 68°F, with 3.3 in of rain across 6.8 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 8th-wettest month of the year here.

Highs ease over the month, from about 89°F in the first days to 82°F by the end. The sky is clear or mostly clear about 55% of the time in September, and the air most often feels muggy.

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 Denison's 1st-clearest and 11th-windiest month. For the whole year in context, see Denison's year-round climate.

Daytime high
85°
4th warmest
Overnight low
68°
9th coldest
Rainfall
3.3 in
6.8 wet days
Daylight
12 h 12 min
6:14 AM – 6:27 PM
Cloud cover
41%
1st clearest
Wind
6 mph
11th windiest
Solar energy
5.09 kWh/m²
Travel score
5.8
out of 10

Denison is city in Grayson County, Texas, United States.

Density
381/km²
people per km²
Founded
1872

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 89°F in the first days to 82°F by the end.

A typical September day in Denison reaches about 85°F in the afternoon and slips back to 68°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 77°F and 93°F. Set against its neighbours, September runs about 7°F cooler than August and about 10°F warmer than October.

60°80°100°151015202530
Avg high (°F)Avg low (°F)
19073
29072
38972
48972
58971
68971
78871
88870
98770
108770
118769
128769
138669
148668
158568
168568
178567
188567
198467
208466
218466
228365
238365
248365
258364
268264
278263
288263
298263
308162

How September really feels in Denison

Once humidity and wind are folded in, September averages 7 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
7
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.

Denison weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan53° / 36°2.56.70.7103.4
Feb58° / 40°2.67.20.710.74.5
Mar65° / 47°4.09.40.411.76.1
Apr73° / 55°4.69.1012.87.0
May80° / 64°6.011.9013.76.2
Jun88° / 72°3.78.8014.24.6
Jul93° / 75°2.06.30143.6
Aug92° / 75°2.05.8013.33.6
Sep85° / 68°3.36.8012.25.8
Oct75° / 56°4.27.9011.27.4
Nov64° / 46°3.47.10.110.26.2
Dec55° / 38°3.36.90.49.83.8

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 55% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 30%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17228
27129
37129
47030
57030
66832
76832
86832
96733
106733
116634
126733
136733
146733
156634
166634
176733
186733
196832
206931
217030
227129
237228
247327
257426
267426
277426
287426
297426
307327

Chance of precipitation in September

Any precipitation

Denison gets around 3.3 in of rain over 6.8 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 23% and peaks near 26% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%151015202530
Rain chance (%)
122
223
323
424
525
625
726
826
926
1026
1126
1226
1326
1426
1526
1626
1725
1825
1924
2023
2122
2221
2320
2419
2518
2617
2717
2817
2917
3018

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels muggy — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the muggy band about 32% of days. Sticky, muggy-or-worse air turns up on roughly 50% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
148223928
248223827
359223827
469213726
5710213725
6810213725
7811203724
8911193724
91011193723
101112183723
111112173722
121212173622
131313173621
141413173620
151413173620
161514173519
171614173518
181714173417
191915173317
202015173216
212216173015
222316182914
232517182713
242717182612
252818192411
263018192310
273118192110
28331920209
29351920198
30361920187

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
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm

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 6:04 AM to 6:24 AM, and sunset from 6:48 PM to 6:07 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.76:046:48
212.76:046:47
312.76:056:45
412.66:066:44
512.66:076:42
612.66:076:41
712.56:086:40
812.56:096:38
912.56:096:37
1012.46:106:35
1112.46:116:34
1212.36:116:32
1312.36:126:31
1412.36:136:30
1512.26:146:28
1612.26:146:27
1712.26:156:25
1812.16:166:24
1912.16:166:22
2012.16:176:21
2112.06:186:19
2212.06:196:18
2312.06:196:17
2411.96:206:15
2511.96:216:14
2611.86:216:12
2711.86:226:11
2811.86:236:09
2911.76:246:08
3011.76:246:07

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.09 kWh/m².

For context, solar energy here swings from a low near 2.48 kWh/m² to a high of 6.76 kWh/m² in July across the year — September's 5.09 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.6Bright
25.6Bright
35.5Bright
45.5Bright
55.4Bright
65.4Bright
75.3Bright
85.3Bright
95.3Bright
105.2Bright
115.2Bright
125.1Bright
135.1Bright
145.1Bright
155.0Bright
165.0Bright
175.0Bright
185.0Bright
195.0Bright
204.9Bright
214.9Bright
224.9Bright
234.9Bright
244.9Bright
254.8Bright
264.8Bright
274.8Bright
284.8Bright
294.8Bright
304.7Bright
Planning a trip in September

Is September a good time to visit Denison?

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

5.8
Sightseeing
6th-best month of the year
7.5
Beach & pool
1st-best month of the year

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

What to pack for Denison in September

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

In September, Denison sees daytime highs around 85°F and nights near 68°F. Pack light clothes. Worth having: sun protection. About 7 days see rain.

light clothessun protection

UV index in Denison in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Denison peaks around June 20 at about 10 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 3 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJun 20UV 10Dec 22UV 3
UV index (midday)Level
Jan3Moderate
Feb5Moderate
Mar6High
Apr9Very high
May9Very high
Jun10Extreme
Jul10Very high
Aug10Very high
Sep8Very high
Oct6High
Nov4Moderate
Dec3Moderate

Air quality in Denison 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 Denison is worst in July — around 18 µg/m³ PM2.5 (moderate), about 3.1× the cleanest month (November, 6 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1618 µg/m³Nov 216 µg/m³
PM2.5 (µg/m³)Level
Jan6Good
Feb8Good
Mar10Good
Apr10Good
May13Moderate
Jun15Moderate
Jul18Moderate
Aug14Moderate
Sep10Good
Oct6Good
Nov6Good
Dec6Good
Location & terrain

Where is Denison?

Denison sits at 33.8°N, 96.5°W, 728 ft above sea level, in United States. The nearest listed city is Sherman, 9.3 mi away.

Topography around Denison

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

Within 2 miles, the terrain around Denison has only modest variations in elevation — a maximum elevation change of 256 ft around an average of 709 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 449 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 768 ft.

The land around Denison is covered by trees (63%) and grassland (21%) within 2 miles, grassland (45%) and trees (38%) within 10 miles, and grassland (53%) and trees (32%) within 50 miles.

2 miles
256 ft
10 miles
449 ft
50 miles
768 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Sherman 9.3 mi · Durant 19 mi · Celina 33 mi · Gainesville 35 mi · McKinney 39 mi · Prosper 39 mi · Frisco 45 mi · Ardmore 45 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 Denison (33.7557°, -96.5367°, elevation 728 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).