Round Rock weather in September

In September, Round Rock sees average daytime highs of 89°F and overnight lows near 69°F, with 2.9 in of rain across 7.4 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 5th-wettest month of the year here.

Highs ease over the month, from about 92°F in the first days to 86°F by the end. The sky is clear or mostly clear about 52% of the time in September, and the air most often feels muggy.

Daylight stretches from about 12 h 36 min at the start of September to 11 h 42 min by month's end. Set against the rest of the year, September is Round Rock's 2nd-clearest and 12th-windiest month. For the whole year in context, see Round Rock's year-round climate.

Daytime high
89°
4th warmest
Overnight low
69°
9th coldest
Rainfall
2.9 in
7.4 wet days
Daylight
12 h 12 min
6:20 AM – 6:31 PM
Cloud cover
44%
2nd clearest
Wind
6 mph
12th windiest
Solar energy
5.17 kWh/m²
Travel score
4.6
out of 10

Round Rock is city in Travis and Williamson counties in Texas, United States.

Density
1,249/km²
people per km²
Founded
1851

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 92°F in the first days to 86°F by the end.

A typical September day in Round Rock reaches about 89°F in the afternoon and slips back to 69°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 81°F and 96°F. Set against its neighbours, September runs about 6°F cooler than August and about 9°F warmer than October.

60°80°100°151015202530
Avg high (°F)Avg low (°F)
19273
29273
39273
49273
59172
69172
79172
89172
99071
109071
119071
128971
138970
148970
158970
168869
178869
188869
198869
208868
218768
228767
238767
248767
258767
268666
278666
288665
298665
308565

How September really feels in Round Rock

Once humidity and wind are folded in, September averages 18 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
18
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.

Round Rock weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan60° / 41°2.36.810.35.4
Feb64° / 45°2.47.310.96.2
Mar71° / 51°2.98.811.86.9
Apr78° / 58°3.08.212.77.1
May85° / 66°4.310.813.55.3
Jun91° / 73°2.88.713.93.8
Jul95° / 75°1.65.813.82.9
Aug95° / 75°2.15.813.12.9
Sep89° / 69°2.97.412.24.6
Oct80° / 60°3.47.111.37.1
Nov69° / 50°2.76.610.57.1
Dec62° / 43°2.87.510.15.7

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 52% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 30%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17030
26931
36931
46832
56733
66634
76634
86535
96535
106535
116535
126535
136535
146535
156535
166634
176733
186832
196931
207030
217129
227327
237426
247525
257624
267723
277723
287822
297822
307723

Chance of precipitation in September

Any precipitation

Round Rock gets around 2.9 in of rain over 7.4 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 25% and peaks near 28% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%151015202530
Rain chance (%)
125
225
326
426
527
627
727
828
928
1028
1128
1228
1328
1428
1528
1627
1727
1826
1925
2025
2124
2223
2322
2421
2521
2620
2720
2819
2919
3019

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 33% of days. Sticky, muggy-or-worse air turns up on roughly 62% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1361641331
2461740331
3461740321
4571739321
5571739321
6671738311
7671638321
8761638331
9761637331
10861537341
11861536340
12971536340
13971535340
141071534340
151071534330
161181533330
171281532320
181391631310
1914101630300
2015101630290
2116111629280
2218121628260
2319131627250
2421131626230
2522141726220
2623141725200
2724151725190
2825151725180
2926151724170
3028151724160

Wind in September

Winds average 6 mph in September, the calmest month.

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
176calm
186calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 36 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 54 minutes over September. Sunrise moves from 6:11 AM to 6:28 AM, and sunset from 6:50 PM to 6:12 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.66:116:50
212.66:126:49
312.66:126:47
412.66:136:46
512.56:136:45
612.56:146:44
712.56:146:42
812.46:156:41
912.46:166:40
1012.46:166:38
1112.36:176:37
1212.36:176:36
1312.36:186:34
1412.26:186:33
1512.26:196:32
1612.26:206:31
1712.26:206:29
1812.16:216:28
1912.16:216:27
2012.16:226:25
2112.06:226:24
2212.06:236:23
2312.06:246:21
2411.96:246:20
2511.96:256:19
2611.96:256:17
2711.86:266:16
2811.86:276:15
2911.86:276:13
3011.76:286:12

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.17 kWh/m².

For context, solar energy here swings from a low near 2.69 kWh/m² to a high of 6.77 kWh/m² in July across the year — September's 5.17 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.7Bright
25.6Bright
35.6Bright
45.5Bright
55.5Bright
65.4Bright
75.4Bright
85.3Bright
95.3Bright
105.2Bright
115.2Bright
125.2Bright
135.1Bright
145.1Bright
155.1Bright
165.1Bright
175.1Bright
185.0Bright
195.0Bright
205.0Bright
215.0Bright
225.0Bright
235.0Bright
245.0Bright
255.0Bright
265.0Bright
274.9Bright
284.9Bright
294.9Bright
304.8Bright
Planning a trip in September

Is September a good time to visit Round Rock?

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

4.6
Sightseeing
9th-best month of the year
7.1
Beach & pool
2nd-best month of the year

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

What to pack for Round Rock in September

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

In September, Round Rock sees daytime highs around 89°F and nights near 69°F. Pack light clothes. Worth having: sun protection. About 7 days see rain.

light clothessun protection

UV index in Round Rock in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Round Rock peaks around July 24 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 4 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJul 24UV 11Dec 20UV 4
UV index (midday)Level
Jan4Moderate
Feb6High
Mar7High
Apr10Very high
May10Extreme
Jun10Extreme
Jul11Extreme
Aug11Extreme
Sep8Very high
Oct6High
Nov5Moderate
Dec4Moderate

Air quality in Round Rock 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 Round Rock is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.7× the cleanest month (December, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1417 µg/m³Dec 127 µg/m³
PM2.5 (µg/m³)Level
Jan7Good
Feb7Good
Mar9Good
Apr10Good
May14Moderate
Jun15Moderate
Jul18Moderate
Aug13Moderate
Sep10Good
Oct7Good
Nov7Good
Dec7Good
Location & terrain

Where is Round Rock?

Round Rock sits at 30.5°N, 97.7°W, 735 ft above sea level, in United States. The nearest listed city is Brushy Creek, 3.7 mi away.

Topography around Round Rock

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

Within 2 miles, the terrain around Round Rock has only modest variations in elevation — a maximum elevation change of 220 ft around an average of 751 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 1,519 ft.

The land around Round Rock is covered by artificial surfaces (50%) and trees (32%) within 2 miles, trees (31%), grassland (30%) and artificial surfaces (29%) within 10 miles, and grassland (44%) and trees (42%) within 50 miles.

2 miles
220 ft
10 miles
492 ft
50 miles
1,519 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Brushy Creek 3.7 mi · Pflugerville 6.2 mi · Jollyville 7.5 mi · Hutto 8.1 mi · Cedar Park 8.7 mi · Georgetown 8.7 mi · Leander 11 mi · University of Texas 16 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 Round Rock (30.5083°, -97.6789°, elevation 735 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).