Monroe weather in September

In September, Monroe sees average daytime highs of 68°F and overnight lows near 49°F, with 3.7 in of rain across 9.2 wet days and about 12.4 hours of daylight. It is the 3rd-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 71°F in the first days to 65°F by the end. The sky is clear or mostly clear about 40% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 12 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Monroe's 3rd-clearest and 9th-windiest month. For the whole year in context, see Monroe's year-round climate.

Daytime high
68°
3rd warmest
Overnight low
49°
9th coldest
Rainfall
3.7 in
9.2 wet days
Daylight
12 h 18 min
5:52 AM – 6:12 PM
Cloud cover
49%
3rd clearest
Wind
4 mph
9th windiest
Solar energy
4.01 kWh/m²
Travel score
6.5
out of 10

Monroe is city in Snohomish County, Washington, United States.

Density
1,144/km²
people per km²
Founded
1903

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 71°F in the first days to 65°F by the end.

A typical September day in Monroe reaches about 68°F in the afternoon and slips back to 49°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 60°F and 78°F. Set against its neighbours, September runs about 6°F cooler than August and about 10°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17152
27152
37152
47151
57151
67051
77051
87051
97051
106951
116951
126950
136950
146850
156850
166850
176849
186749
196749
206749
216749
226648
236648
246648
256548
266547
276547
286547
296447
306446

How September really feels in Monroe

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.

Monroe weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan45° / 36°9.01948.60.8
Feb48° / 36°6.115.52.99.91.5
Mar52° / 38°7.119.12.311.62.2
Apr57° / 41°5.916.70.313.43.4
May63° / 46°4.113.2014.95.1
Jun67° / 51°3.511.4015.75.9
Jul73° / 54°1.66.3015.47.6
Aug74° / 54°1.85.7014.17.8
Sep68° / 49°3.79.2012.46.5
Oct58° / 43°7.415.3010.63.8
Nov49° / 38°9.919.10.99.11.6
Dec44° / 35°8.718.73.98.30.6

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 40% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 15% of September, with mostly cloudy or overcast conditions the remaining 45%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15941
25842
35842
45941
55941
65941
75941
85842
95842
105743
115644
125644
135545
145545
155446
165545
175446
185446
195446
205446
215347
225446
235347
245347
255347
265347
275347
285248
295248
305050

Chance of precipitation in September

Any precipitation

Monroe gets around 3.7 in of rain over 9.2 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 31% and peaks near 34% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%151015202530
Rain chance (%)
126
226
327
427
527
628
728
828
929
1030
1131
1231
1332
1432
1533
1633
1733
1833
1934
2034
2134
2234
2334
2434
2533
2633
2733
2833
2933
3034

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 81% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
171281
272271
372271
473261
574251
674251
775241
876231
977221
1077221
1178211
1279201
1379201
1480191
1580191
1681181
1782171
1882171
1983161
2084151
2184151
2285141
2386131
2487121
2587121
2688111
2789101
289190
299280
309280

Wind in September

Winds average 4 mph in September.

Across September, daily wind ranges from about 4 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 12 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 102 minutes over September. Sunrise moves from 5:31 AM to 6:12 AM, and sunset from 6:44 PM to 5:43 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.25:316:44
213.25:326:42
313.15:346:40
413.05:356:38
513.05:376:36
612.95:386:34
712.95:396:32
812.85:416:30
912.85:426:27
1012.75:446:25
1112.65:456:23
1212.65:466:21
1312.55:486:19
1412.55:496:17
1512.45:516:15
1612.35:526:12
1712.35:536:10
1812.25:556:08
1912.25:566:06
2012.15:586:04
2112.05:596:02
2212.06:006:00
2311.96:025:57
2411.96:035:55
2511.86:055:53
2611.76:065:51
2711.76:085:49
2811.66:095:47
2911.66:105:45
3011.56:125:43

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.01 kWh/m².

For context, solar energy here swings from a low near 0.86 kWh/m² to a high of 6.13 kWh/m² in July across the year — September's 4.01 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.7Bright
34.6Bright
44.6Bright
54.5Bright
64.5Bright
74.4Bright
84.4Bright
94.3Bright
104.3Bright
114.2Bright
124.2Bright
134.1Bright
144.0Bright
154.0Moderate
163.9Moderate
173.9Moderate
183.8Moderate
193.8Moderate
203.7Moderate
213.7Moderate
223.6Moderate
233.6Moderate
243.5Moderate
253.5Moderate
263.4Moderate
273.4Moderate
283.3Moderate
293.2Moderate
303.2Moderate
Planning a trip in September

Hazard calendar for Monroe

In seasonPeak

None of Monroe's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Monroe's rainy season runs October–April, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Monroe?

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

6.5
Sightseeing
3rd-best month of the year
3.4
Beach & pool
3rd-best month of the year

September is a reasonable time to visit Monroe for sightseeing.

What to pack for Monroe in September

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

In September, Monroe sees daytime highs around 68°F and nights near 49°F. Worth packing: rain gear. About 9 days see rain.

rain gear

UV index in Monroe in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Monroe peaks around July 17 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 18 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 17UV 8Dec 18UV 1
UV index (midday)Level
Jan1Low
Feb1Low
Mar4Moderate
Apr5Moderate
May7High
Jun6High
Jul8Very high
Aug6High
Sep4Moderate
Oct3Moderate
Nov1Low
Dec1Low

Air quality in Monroe 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 Monroe is worst in August — around 20 µg/m³ PM2.5 (moderate), about 3.1× the cleanest month (December, 6 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodGoodModerateGoodModerateGoodAug 2119 µg/m³Dec 157 µg/m³
PM2.5 (µg/m³)Level
Jan8Good
Feb10Good
Mar12Moderate
Apr12Good
May13Moderate
Jun11Good
Jul10Good
Aug20Moderate
Sep18Moderate
Oct11Good
Nov7Good
Dec6Good
Location & terrain

Where is Monroe?

Monroe sits at 47.9°N, 122.0°W, 72 ft above sea level, in United States. The nearest listed city is Silver Firs, 8.7 mi away.

Topography around Monroe

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

Within 2 miles, the terrain around Monroe has only modest variations in elevation — a maximum elevation change of 600 ft around an average of 138 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,808 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 10,427 ft.

The land around Monroe is covered by trees (49%) and grassland (28%) within 2 miles, trees (77%) within 10 miles, and trees (74%) within 50 miles.

2 miles
600 ft
10 miles
2,808 ft
50 miles
10,427 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Silver Firs 8.7 mi · Cottage Lake 9.3 mi · North Creek 9.9 mi · Mill Creek East 9.9 mi · Eastmont 9.9 mi · Mill Creek 11 mi · West Lake Stevens 11 mi · Lake Stevens 12 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 Monroe (47.8554°, -121.971°, elevation 72 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).