Hermiston weather in September

In September, Hermiston sees average daytime highs of 79°F and overnight lows near 55°F, with 0.3 in of rain across 2.2 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 84°F in the first days to 74°F by the end. The sky is clear or mostly clear about 62% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 06 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Hermiston's 3rd-clearest and 8th-windiest month. For the whole year in context, see Hermiston's year-round climate.

Daytime high
79°
4th warmest
Overnight low
55°
9th coldest
Rainfall
0.3 in
2.2 wet days
Daylight
12 h 18 min
5:42 AM – 6:01 PM
Cloud cover
33%
3rd clearest
Wind
6 mph
8th windiest
Solar energy
5.09 kWh/m²
Travel score
8.1
out of 10

Hermiston is city in Oregon, USA.

Density
815/km²
people per km²
Founded
1907

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 84°F in the first days to 74°F by the end.

A typical September day in Hermiston reaches about 79°F in the afternoon and slips back to 55°F overnight — a 24°F spread between the day's warmth and the night's chill. On most days the high lands between 69°F and 90°F. Set against its neighbours, September runs about 10°F cooler than August and about 15°F warmer than October.

40°60°80°100°151015202530
Avg high (°F)Avg low (°F)
18559
28459
38458
48458
58358
68358
78357
88257
98257
108256
118156
128156
138056
148055
158055
167955
177955
187854
197854
207854
217753
227753
237653
247652
257652
267552
277551
287451
297451
307351

How September really feels in Hermiston

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.

Hermiston 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 daysSnow daysDaylight (hours)Travel score
Jan42° / 31°1.59.52.28.90.3
Feb48° / 33°1.27.71.510.11.8
Mar56° / 38°1.38.30.311.64.0
Apr65° / 44°1.06.3013.36.2
May74° / 51°0.95.4014.77.6
Jun81° / 57°0.63.3015.57.4
Jul91° / 63°0.11015.24.9
Aug89° / 62°0.21013.95.3
Sep79° / 55°0.32.2012.38.1
Oct65° / 45°1.05.90.110.76.5
Nov50° / 36°1.48.70.79.32.3
Dec42° / 31°1.69.62.68.50.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 62% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 24%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
18515
28515
38515
48317
58317
68317
78119
88119
98020
107822
117822
127723
137624
147624
157426
167426
177327
187327
197228
207228
217129
227228
237129
247129
257228
267129
277129
287030
297030
307030

Chance of precipitation in September

Any precipitation

Hermiston gets around 0.3 in of rain over 2.2 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 8% and peaks near 12% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%151015202530
Rain chance (%)
14
24
34
44
54
64
75
85
96
106
116
127
137
147
158
168
178
188
199
209
219
229
2310
2410
2510
2610
2710
2811
2911
3012

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 99% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)
1991
2991
3991
4991
5991
6991
7991
8991
9991
10991
11991
12991
13991
14991
15991
16991
17991
18991
19991
20991
21991
22991
23991
24991
25991
26991
27991
28991
29991
30991

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
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
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 13 h 06 min at the start of September to 11 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 96 minutes over September. Sunrise moves from 5:23 AM to 6:00 AM, and sunset from 6:31 PM to 5:33 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:236:31
213.15:246:29
313.05:256:27
413.05:276:25
512.95:286:23
612.95:296:21
712.85:306:19
812.85:326:17
912.75:336:15
1012.65:346:13
1112.65:366:11
1212.55:376:09
1312.55:386:07
1412.45:396:05
1512.45:416:03
1612.35:426:01
1712.35:435:59
1812.25:455:57
1912.25:465:55
2012.15:475:53
2112.05:485:51
2212.05:505:49
2311.95:515:47
2411.95:525:45
2511.85:545:43
2611.85:555:41
2711.75:565:39
2811.75:585:37
2911.65:595:35
3011.56:005:33

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 1.29 kWh/m² to a high of 7.88 kWh/m² in July across the year — September's 5.09 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.0Bright
25.9Bright
35.9Bright
45.8Bright
55.8Bright
65.7Bright
75.6Bright
85.6Bright
95.5Bright
105.4Bright
115.4Bright
125.3Bright
135.3Bright
145.2Bright
155.1Bright
165.1Bright
175.0Bright
184.9Bright
194.9Bright
204.8Bright
214.7Bright
224.7Bright
234.6Bright
244.5Bright
254.5Bright
264.4Bright
274.4Bright
284.3Bright
294.2Bright
304.2Bright
Planning a trip in September

Is September a good time to visit Hermiston?

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

8.1
Sightseeing
1st-best month of the year
7.9
Beach & pool
3rd-best month of the year

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

What to pack for Hermiston in September

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

In September, Hermiston sees daytime highs around 79°F and nights near 55°F. Worth packing: light clothes and sun protection.

light clothessun protection

UV index in Hermiston in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Hermiston peaks around July 16 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 15 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 16UV 8Dec 15UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar4Moderate
Apr5Moderate
May7Very high
Jun7High
Jul8Very high
Aug6High
Sep5Moderate
Oct4Moderate
Nov1Low
Dec1Low

Air quality in Hermiston 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 Hermiston is worst in August — around 25 µg/m³ PM2.5 (moderate), about 3.5× the cleanest month (December, 7 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodAug 1924 µg/m³Dec 217 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb9Good
Mar11Good
Apr10Good
May9Good
Jun9Good
Jul15Moderate
Aug25Moderate
Sep20Moderate
Oct11Good
Nov10Good
Dec7Good
Location & terrain

Where is Hermiston?

Hermiston sits at 45.8°N, 119.3°W, 459 ft above sea level, in United States. The nearest listed city is Kennewick, 27 mi away.

Topography around Hermiston

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

Within 2 miles, the terrain around Hermiston has only modest variations in elevation — a maximum elevation change of 236 ft around an average of 509 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 932 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 5,659 ft.

The land around Hermiston is covered by grassland (45%) and artificial surfaces (29%) within 2 miles, grassland (45%) and cropland (41%) within 10 miles, and grassland (54%) and cropland (35%) within 50 miles.

2 miles
236 ft
10 miles
932 ft
50 miles
5,659 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Kennewick 27 mi · Pendleton 27 mi · Tri-Cities 29 mi · Pasco 29 mi · Richland 31 mi · Sunnyside 48 mi · Walla Walla 48 mi · Yakima 78 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 Hermiston (45.8404°, -119.2895°, elevation 459 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).