Ottawa weather in August

In August, Ottawa sees average daytime highs of 82°F and overnight lows near 64°F, with 3.5 in of rain across 9.7 wet days and about 13.7 hours of daylight. It is the 2nd-warmest and 5th-wettest month of the year here.

Day-to-day highs hold fairly steady near 82°F through the month. The sky is clear or mostly clear about 39% of the time in August, and the air most often feels humid.

Daylight stretches from about 14 h 12 min at the start of August to 13 hours by month's end. Set against the rest of the year, August is Ottawa's 2nd-clearest and 12th-windiest month. For the whole year in context, see Ottawa's year-round climate.

Daytime high
82°
2nd warmest
Overnight low
64°
11th coldest
Rainfall
3.5 in
9.7 wet days
Daylight
13 h 42 min
5:09 AM – 6:50 PM
Cloud cover
53%
2nd clearest
Wind
6 mph
12th windiest
Solar energy
5.56 kWh/m²
Travel score
6.6
out of 10

Ottawa is city in Illinois, United States.

Density
553/km²
people per km²
Founded
1853

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in August

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 82°F through the month.

A typical August day in Ottawa reaches about 82°F in the afternoon and slips back to 64°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 74°F and 89°F. Set against its neighbours, August runs about 2°F cooler than July and about 6°F warmer than September.

50°60°70°80°90°151015202531
Avg high (°F)Avg low (°F)
18265
28265
38265
48265
58264
68264
78264
88264
98264
108264
118264
128264
138264
148164
158164
168164
178163
188163
198163
208163
218163
228163
238163
248163
258163
268163
278162
288162
298162
308162
318162

How August really feels in Ottawa

Once humidity and wind are folded in, August 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

August sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Ottawa weather by month

How August compares with the rest of the year at a glance. August is the 2nd-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan32° / 18°2.28.25.49.40.0
Feb37° / 21°2.07.24.210.30.0
Mar49° / 31°2.89.92.411.71.9
Apr61° / 41°4.311.90.613.14.8
May71° / 52°4.713014.36.1
Jun80° / 62°4.411.7014.96.2
Jul83° / 66°3.811.3014.75.7
Aug82° / 64°3.59.7013.76.6
Sep76° / 56°3.18.4012.37.1
Oct63° / 44°3.190.110.95.7
Nov49° / 33°2.78.61.19.72.1
Dec37° / 23°2.28.13.79.10.0

Cloud cover in August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 39% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 17% of August, with mostly cloudy or overcast conditions the remaining 44%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15743
25842
35842
45842
55842
65743
75743
85743
95644
105644
115644
125644
135644
145644
155545
165545
175545
185644
195644
205545
215545
225545
235446
245545
255545
265545
275644
285743
295743
305743
315941

Chance of precipitation in August

Any precipitation

Ottawa gets around 3.5 in of rain over 9.7 wet days in August. 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 32% on the wettest days.

0%10%20%30%40%151015202531
Rain chance (%)
131
231
331
430
530
630
730
830
930
1030
1130
1230
1331
1431
1531
1631
1731
1831
1932
2032
2132
2232
2332
2432
2531
2631
2730
2830
2930
3029
3129

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, August lands in the humid band about 26% of days. Sticky, muggy-or-worse air turns up on roughly 40% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
17212626181
27212626181
37222626181
47222625181
58222625181
68232624171
78232624171
89232624171
99232624171
1010232624161
1110232624161
1210232624151
1311232624151
1411232624151
1511232624141
1612222624141
1712222625141
1812222625141
1912212626131
2012212627131
2112202627131
2213202628131
2313202628121
2413212528121
2513212527121
2614212527121
2715222526111
2816222526111
2917222525100
3018232524100
311923252490

Wind in August

Winds average 6 mph in August, the calmest month.

Across August, 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.

0246810151015202531
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm
317calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 h 12 min at the start of August to 13 hours by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 72 minutes over August. Sunrise moves from 4:54 AM to 5:25 AM, and sunset from 7:09 PM to 6:26 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.24:547:09
214.24:557:08
314.24:567:07
414.14:577:05
514.14:587:04
614.14:597:03
714.05:007:02
814.05:017:01
914.05:026:59
1013.95:036:58
1113.95:046:57
1213.85:056:55
1313.85:066:54
1413.85:076:52
1513.75:086:51
1613.75:096:50
1713.65:106:48
1813.65:116:47
1913.55:126:45
2013.55:136:44
2113.55:156:42
2213.45:166:41
2313.45:176:39
2413.35:186:37
2513.35:196:36
2613.25:206:34
2713.25:216:33
2813.25:226:31
2913.15:236:29
3013.15:246:28
3113.05:256:26

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.56 kWh/m².

For context, solar energy here swings from a low near 1.72 kWh/m² to a high of 6.31 kWh/m² in June across the year — August's 5.56 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
16.0Intense
26.0Bright
36.0Bright
45.9Bright
55.9Bright
65.9Bright
75.8Bright
85.8Bright
95.8Bright
105.7Bright
115.7Bright
125.7Bright
135.6Bright
145.6Bright
155.6Bright
165.5Bright
175.5Bright
185.5Bright
195.5Bright
205.4Bright
215.4Bright
225.4Bright
235.3Bright
245.3Bright
255.3Bright
265.3Bright
275.2Bright
285.2Bright
295.2Bright
305.2Bright
315.1Bright
Planning a trip in August

Is August a good time to visit Ottawa?

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

6.6
Sightseeing
2nd-best month of the year
6.9
Beach & pool
1st-best month of the year

August is a reasonable time to visit Ottawa for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Ottawa in August

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

In August, Ottawa sees daytime highs around 82°F and nights near 64°F. Pack light clothes. Worth having: rain gear and sun protection. About 10 days see rain.

light clothesrain gearsun protection

UV index in Ottawa in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Ottawa peaks around June 20 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJun 20UV 9Dec 19UV 2
UV index (midday)Level
Jan2Moderate
Feb3Moderate
Mar5Moderate
Apr6High
May7Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Ottawa in August

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where August falls, not just the annual average.

Air quality in Ottawa is worst in July — around 17 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (October, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodJul 1917 µg/m³Oct 229 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb14Moderate
Mar14Moderate
Apr13Moderate
May14Moderate
Jun15Moderate
Jul17Moderate
Aug16Moderate
Sep12Moderate
Oct9Good
Nov9Good
Dec10Good
Location & terrain

Where is Ottawa?

Ottawa sits at 41.3°N, 88.8°W, 482 ft above sea level, in United States. The nearest listed city is Yorkville, 29 mi away.

Topography around Ottawa

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

Within 2 miles, the terrain around Ottawa has only modest variations in elevation — a maximum elevation change of 295 ft around an average of 531 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 417 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 692 ft.

The land around Ottawa is covered by trees (36%) and artificial surfaces (24%) within 2 miles, cropland (69%) within 10 miles, and cropland (78%) within 50 miles.

2 miles
295 ft
10 miles
417 ft
50 miles
692 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
August weather nearby: Yorkville 29 mi · Oswego 34 mi · Shorewood 35 mi · Montgomery 37 mi · Plainfield 39 mi · Aurora 39 mi · DeKalb 40 mi · Crest Hill 41 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 Ottawa (41.3456°, -88.8426°, elevation 482 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).