Harlingen weather in September

In September, Harlingen sees average daytime highs of 91°F and overnight lows near 75°F, with 4.1 in of rain across 14.4 wet days and about 12.2 hours of daylight. It is the 4th-warmest and 1st-wettest month of the year here.

Highs ease over the month, from about 93°F in the first days to 89°F by the end. The sky is clear or mostly clear about 41% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 12 h 30 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Harlingen's 8th-clearest and 12th-windiest month. For the whole year in context, see Harlingen's year-round climate.

Daytime high
91°
4th warmest
Overnight low
75°
9th coldest
Rainfall
4.1 in
14.4 wet days
Daylight
12 h 12 min
6:21 AM – 6:30 PM
Cloud cover
53%
8th clearest
Wind
8 mph
12th windiest
Solar energy
5.18 kWh/m²
Travel score
3.4
out of 10

Harlingen is city in Cameron County, Texas, United States.

Density
630/km²
people per km²
Founded
1904

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 89°F by the end.

A typical September day in Harlingen reaches about 91°F in the afternoon and slips back to 75°F overnight — a 16°F spread between the day's warmth and the night's chill. On most days the high lands between 85°F and 96°F. Set against its neighbours, September runs about 5°F cooler than August and about 5°F warmer than October.

60°70°80°90°100°151015202530
Avg high (°F)Avg low (°F)
19377
29377
39377
49376
59276
69276
79276
89276
99276
109176
119176
129176
139175
149175
159175
169175
179075
189074
199074
209074
219074
229074
239073
249073
258973
268973
278973
288972
298972
308972

How September really feels in Harlingen

Once humidity and wind are folded in, September averages 30 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
30
6 feel dangerously hot (≥ 102°F)
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.

Harlingen weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan71° / 53°1.25.110.57.3
Feb75° / 57°1.04.911.17.6
Mar80° / 62°1.65.511.87.2
Apr85° / 68°1.75.512.65.7
May90° / 73°1.96.513.34.3
Jun94° / 77°2.38.913.63.1
Jul95° / 78°2.48.513.52.6
Aug95° / 78°2.19.412.92.5
Sep91° / 75°4.114.412.23.4
Oct86° / 68°2.77.911.45.5
Nov78° / 61°1.56.510.77.4
Dec73° / 55°1.35.510.47.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 41% 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 41%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15644
25644
35545
45446
55446
65446
75347
85347
95347
105446
115446
125446
135545
145545
155644
165644
175842
185842
195941
206040
216139
226337
236436
246535
256634
266733
276931
286931
297030
307030

Chance of precipitation in September

Any precipitation

Harlingen gets around 4.1 in of rain over 14.4 wet days in September, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 47% and peaks near 56% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
148
250
351
452
554
654
755
856
956
1055
1155
1254
1353
1452
1550
1649
1748
1847
1946
2044
2143
2241
2339
2438
2537
2636
2735
2834
2934
3033

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the oppressive band about 49% of days. Sticky, muggy-or-worse air turns up on roughly 91% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
100166033
200175834
300175834
400175735
500175735
600275536
701275436
801275337
901275337
1001275238
1101375138
1201375138
1301375138
1401485038
1501484937
1601594936
1701694836
18016104835
19127104733
20128114632
21139124530
221310124529
231310134528
241411144426
251412154324
262512164322
272513174321
282513174320
292614184218
302614184217

Wind in September

Winds average 8 mph in September, the calmest month.

Across September, daily wind ranges from about 8 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
18light breeze
28light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
108light breeze
118light breeze
128light breeze
138light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
308light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 30 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 42 minutes over September. Sunrise moves from 6:14 AM to 6:27 AM, and sunset from 6:47 PM to 6:14 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.56:146:47
212.56:156:46
312.56:156:45
412.56:166:43
512.46:166:42
612.46:166:41
712.46:176:40
812.46:176:39
912.36:186:38
1012.36:186:37
1112.36:186:35
1212.36:196:34
1312.26:196:33
1412.26:206:32
1512.26:206:31
1612.26:216:30
1712.16:216:29
1812.16:216:27
1912.16:226:26
2012.06:226:25
2112.06:236:24
2212.06:236:23
2312.06:246:22
2411.96:246:20
2511.96:246:19
2611.96:256:18
2711.96:256:17
2811.86:266:16
2911.86:266:15
3011.86:276:14

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.18 kWh/m².

For context, solar energy here swings from a low near 2.91 kWh/m² to a high of 6.72 kWh/m² in July across the year — September's 5.18 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
105.3Bright
115.2Bright
125.2Bright
135.2Bright
145.2Bright
155.2Bright
165.1Bright
175.1Bright
185.1Bright
195.1Bright
205.1Bright
215.1Bright
225.1Bright
235.1Bright
245.1Bright
255.0Bright
265.0Bright
275.0Bright
285.0Bright
295.0Bright
305.0Bright
Planning a trip in September

Hazard calendar for Harlingen

In seasonPeak

In September, Harlingen sits inside its atlantic hurricane season. The full year is below, with each hazard's peak months called out.

Harlingen sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Harlingen?

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

3.4
Sightseeing
9th-best month of the year
5.8
Beach & pool
8th-best month of the year

September is a weaker month for outdoor sightseeing in Harlingen.

What to pack for Harlingen in September

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

In September, Harlingen sees daytime highs around 91°F and nights near 75°F. Pack light clothes and rain gear. Worth having: sun protection. About 14 days see rain.

light clothesrain gearsun protection

Sea temperature near Harlingen in September

The nearest coast averages about 84°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 35 mi away) is warmest in September at about 84°F and coldest in February near 65°F.

It's comfortable for a long swim from Mar 22 to Dec 29 — about 9.3 months when the water holds above 68°F.

60°70°80°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°F)Comfort
Jan66Cool
Feb65Cool
Mar67Cool
Apr72Refreshing
May77Warm
Jun82Warm
Jul82Tropical
Aug83Tropical
Sep84Tropical
Oct81Warm
Nov75Refreshing
Dec70Refreshing

UV index in Harlingen in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Harlingen peaks around June 21 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 5 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecHighVery highExtremeVery highExtremeVery highHighJun 21UV 12Dec 22UV 5
UV index (midday)Level
Jan5Moderate
Feb7High
Mar8Very high
Apr11Extreme
May9Very high
Jun12Extreme
Jul11Extreme
Aug11Extreme
Sep10Very high
Oct8Very high
Nov6High
Dec5Moderate

Air quality in Harlingen 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 Harlingen is worst in July — around 25 µg/m³ PM2.5 (moderate), about 3.7× the cleanest month (October, 7 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1525 µg/m³Oct 247 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb9Good
Mar11Good
Apr13Moderate
May19Moderate
Jun20Moderate
Jul25Moderate
Aug18Moderate
Sep13Moderate
Oct7Good
Nov7Good
Dec9Good
Location & terrain

Where is Harlingen?

Harlingen sits at 26.2°N, 97.7°W, 39 ft above sea level, in United States. The nearest listed city is San Benito, 5.6 mi away.

Topography around Harlingen

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

Within 2 miles, the terrain around Harlingen has only modest variations in elevation — a maximum elevation change of 66 ft around an average of 43 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 82 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 446 ft.

The land around Harlingen is covered by artificial surfaces (56%) and trees (25%) within 2 miles, cropland (52%) and grassland (22%) within 10 miles, and cropland (34%), grassland (22%) and water (20%) within 50 miles.

2 miles
66 ft
10 miles
82 ft
50 miles
446 ft
treesshrubsgrasslandcroplandartificial surfacesbare terrainwaterwetland
September weather nearby: San Benito 5.6 mi · Mercedes 14 mi · Weslaco 19 mi · Donna 22 mi · Brownsville 24 mi · Heroica Matamoros 25 mi · Alamo 27 mi · Ciudad Río Bravo 28 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 Harlingen (26.1906°, -97.6961°, elevation 39 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).