Harvey weather in September

In September, Harvey sees average daytime highs of 75°F and overnight lows near 56°F, with 3.0 in of rain across 8.5 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 7th-wettest month of the year here.

Highs ease over the month, from about 79°F in the first days to 70°F by the end. The sky is clear or mostly clear about 42% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Harvey's 1st-clearest and 9th-windiest month. For the whole year in context, see Harvey's year-round climate.

Daytime high
75°
4th warmest
Overnight low
56°
9th coldest
Rainfall
3.0 in
8.5 wet days
Daylight
12 h 18 min
5:37 AM – 5:53 PM
Cloud cover
50%
1st clearest
Wind
7 mph
9th windiest
Solar energy
4.59 kWh/m²
Travel score
7.1
out of 10

Harvey is city in Cook County, Illinois, United States.

Density
1,543/km²
people per km²
Founded
1891

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 79°F in the first days to 70°F by the end.

A typical September day in Harvey reaches about 75°F in the afternoon and slips back to 56°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 64°F and 85°F. Set against its neighbours, September runs about 6°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
17961
27961
37961
47960
57860
67860
77859
87759
97758
107758
117658
127657
137657
147556
157556
167556
177455
187455
197454
207354
217354
227353
237253
247252
257152
267152
277151
287051
297051
306950

How September really feels in Harvey

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.

Harvey weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan32° / 19°2.38.75.79.30.0
Feb36° / 21°2.07.14.810.30.0
Mar47° / 31°2.910.6311.71.5
Apr59° / 41°4.412.60.913.14.3
May70° / 51°4.612.6014.36.0
Jun79° / 62°4.311.60156.3
Jul83° / 66°3.911.9014.75.8
Aug81° / 64°3.810.8013.76.5
Sep75° / 56°3.08.5012.37.1
Oct62° / 44°3.29.50.110.95.4
Nov48° / 34°2.78.61.29.71.9
Dec37° / 24°2.283.990.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 42% 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 43%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16040
26040
36040
46139
56139
66139
76139
86139
96139
106040
116040
125941
135842
145842
155842
165743
175743
185644
195644
205644
215644
225545
235545
245545
255446
265446
275347
285347
295347
305347

Chance of precipitation in September

Any precipitation

Harvey gets around 3.0 in of rain over 8.5 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 30% and peaks near 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
131
231
331
430
530
630
730
830
930
1030
1130
1230
1330
1430
1530
1630
1730
1830
1929
2029
2129
2229
2329
2429
2529
2629
2729
2829
2929
3028

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 47% of days. Sticky, muggy-or-worse air turns up on roughly 14% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1202524238
2212624227
3232623217
4252723196
5272822185
6282822175
7302822164
8322821154
9342821143
10362720143
11382720132
12402619122
13422619122
14442518111
15462518111
16482417101
17502416101
1852231591
1955221490
2058211380
2159211280
2261201270
2363191170
2466181060
2566181060
266817960
277016950
287016950
297315840
307414840

Wind in September

Winds average 7 mph in September.

Across September, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187light breeze
197light 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 13 hours at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 84 minutes over September. Sunrise moves from 5:21 AM to 5:52 AM, and sunset from 6:20 PM to 5:28 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.05:216:20
212.95:226:18
312.95:236:16
412.85:246:15
512.85:256:13
612.75:266:11
712.75:276:09
812.75:286:07
912.65:296:06
1012.65:306:04
1112.55:316:02
1212.55:326:00
1312.45:345:59
1412.45:355:57
1512.35:365:55
1612.35:375:53
1712.25:385:51
1812.25:395:50
1912.15:405:48
2012.15:415:46
2112.05:425:44
2212.05:435:42
2311.95:445:41
2411.95:455:39
2511.85:465:37
2611.85:475:35
2711.75:485:33
2811.75:505:32
2911.75:515:30
3011.65:525:28

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.59 kWh/m².

For context, solar energy here swings from a low near 1.66 kWh/m² to a high of 6.5 kWh/m² in June across the year — September's 4.59 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.1Bright
35.1Bright
45.0Bright
55.0Bright
65.0Bright
74.9Bright
84.9Bright
94.8Bright
104.8Bright
114.8Bright
124.7Bright
134.7Bright
144.6Bright
154.6Bright
164.5Bright
174.5Bright
184.5Bright
194.4Bright
204.4Bright
214.3Bright
224.3Bright
234.3Bright
244.2Bright
254.2Bright
264.1Bright
274.1Bright
284.0Bright
294.0Moderate
303.9Moderate
Planning a trip in September

Is September a good time to visit Harvey?

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

7.1
Sightseeing
1st-best month of the year
5.7
Beach & pool
4th-best month of the year

September is one of the better times to visit Harvey for general sightseeing.

What to pack for Harvey in September

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

In September, Harvey sees daytime highs around 75°F and nights near 56°F. Worth packing: light clothes, rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

Sea temperature near Harvey in September

The nearest coast averages about 68°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 14 mi away) is warmest in August at about 73°F and coldest in February near 35°F.

It's comfortable for a long swim from Jul 10 to Sep 16 — about 2.3 months when the water holds above 68°F.

30°40°50°60°70°80°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°F)Comfort
Jan38Bracing
Feb35Bracing
Mar35Bracing
Apr39Bracing
May46Bracing
Jun59Cool
Jul70Refreshing
Aug73Refreshing
Sep68Refreshing
Oct58Bracing
Nov49Bracing
Dec42Bracing

UV index in Harvey in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Harvey peaks around June 23 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJun 23UV 9Jan 1UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May7Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov2Moderate
Dec2Low

Air quality in Harvey 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 Harvey is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1418 µg/m³Oct 238 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb14Moderate
Mar15Moderate
Apr15Moderate
May17Moderate
Jun17Moderate
Jul18Moderate
Aug16Moderate
Sep12Moderate
Oct8Good
Nov9Good
Dec10Good
Location & terrain

Where is Harvey?

Harvey sits at 41.6°N, 87.6°W, 604 ft above sea level, in United States. The nearest listed city is South Holland, 1.9 mi away.

Topography around Harvey

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

Within 2 miles, the terrain around Harvey has only modest variations in elevation — a maximum elevation change of 72 ft around an average of 610 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 509 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 722 ft.

The land around Harvey is covered by artificial surfaces (54%) and trees (29%) within 2 miles, artificial surfaces (48%) and trees (30%) within 10 miles, and cropland (35%) and water (23%) within 50 miles.

2 miles
72 ft
10 miles
509 ft
50 miles
722 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: South Holland 1.9 mi · Dolton 3.1 mi · Blue Island 3.7 mi · Homewood 3.7 mi · Country Club Hills 5.0 mi · Oak Forest 5.0 mi · Morgan Park 5.6 mi · Calumet City 6.2 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 Harvey (41.61°, -87.6467°, elevation 604 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. 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).