Summer in Ottawa means warm days, comfortable evenings, and lots of chances to get outside. Daytime highs usually hit the mid-20s °C (70s °F), with July often bringing the hottest temperatures of the season.
Nights cool off enough to stay pleasant, so you can hang out outdoors from morning until late in the evening.
Rain shows up during the summer months, but it tends to come in short bursts, not all-day storms. This mix of sun and occasional showers keeps the parks and waterways green and pretty inviting.
You’ll also notice daylight stretches well into the evening, so there’s more time to explore.
Humidity and sunshine shift around during the season, but you’ll generally get a mix of bright skies and some cloud cover. Ottawa’s summer climate brings both comfort and variety, making it a great time for outdoor activities, festivals, and sightseeing.
Overview of Ottawa’s Summer Climate
Ottawa’s summer weather brings steady warmth, moderate humidity, and long daylight hours. You’ll get a mix of sunny days, occasional rainfall, and comfortable evenings, all shaped by the city’s continental climate and its spot along the Ottawa River.
Defining Ottawa’s Summer Months
Summer in Ottawa typically runs from June through September. During this stretch, daily highs often reach the mid-70s °F (about 24°C), with the hottest days in July averaging close to 80°F (27°C).
Nights cool off to the mid-50s °F (13°C), so evenings feel much nicer than the daytime.
Rainfall stays pretty steady through the season. You’ll see about 2.5 to 3 inches (65–75 mm) of precipitation each month, usually as quick rain showers or the odd thunderstorm.
Humidity climbs in July, and muggy days do happen, but extreme heat is rare compared to southern regions.
Daylight changes fast. By late June, sunset is close to 9:00 PM, but by late August, it’s before 8:00 PM. That means less time for evening activities as September gets closer.
Climate Classification and Location
Ottawa has a humid continental climate (Dfb), so summers are warm and winters are cold and snowy. Because it’s about 200 km from the Great Lakes, the city doesn’t get much of that moderating lake effect.
This location explains the bigger swings between seasons compared to coastal cities.
At roughly 45°N latitude, Ottawa gets high sun angles in summer, which means long days and strong sunlight in June and July.
By late summer, the sun’s energy drops off, and evenings start to feel cooler.
The Ottawa River valley shapes local weather too. The mostly flat terrain and river corridor help channel winds, keeping air moving and cutting down on extreme humidity.
Winds are generally light in summer, averaging around 4 mph, but they do offer some relief during hot days.
How Ottawa’s Climate Compares to Other Canadian Cities
Ottawa’s summer is warmer than cities like Montreal and Quebec City, which stay a bit cooler and wetter because they’re closer to the St. Lawrence River.
Compared to Toronto, Ottawa is less humid and usually a few degrees cooler, since Toronto’s weather gets influenced by Lake Ontario.
If you look at Winnipeg, Ottawa’s summers are milder. Winnipeg often hits hotter highs and sees more dry spells. Ottawa, on the other hand, keeps steadier rainfall, so things stay greener through July and August.
Now, Vancouver is a whole different story. Vancouver has a maritime climate, so summers are cooler and less humid. Ottawa feels hotter and sunnier, but also gets more thunderstorms and higher rainfall totals during peak summer.
Typical Summer Temperatures in Ottawa
Summer in Ottawa brings warm days and mild nights. Temperatures shift gradually from June through August.
You’ll get steady warmth, but sometimes hot spells push conditions above the seasonal averages.
Average High and Low Temperatures
During summer, daytime highs in Ottawa usually range from the low 70s °F (around 22°C) in early June to the upper 70s °F (25–26°C) in July.
Nights stay cooler, often in the high 50s to low 60s °F (14–17°C).
This balance of warm days and comfortable nights makes it easier to get outside compared to more humid Canadian cities.
July is the warmest month, with average highs near 78°F (26°C).
By late August, temperatures ease a bit. Highs average around 76°F (24°C), and nights dip closer to 61°F (16°C).
You can feel the slow shift toward fall, but there’s still plenty of warm weather left.
Temperature Ranges by Month
Here’s a quick look at typical summer averages in Ottawa:
| Month | Avg High (°F) | Avg Low (°F) |
|---|---|---|
| June | 72 | 57 |
| July | 79 | 63 |
| August | 76 | 61 |
June brings milder conditions paired with long daylight hours. If you like moderate warmth, this is your month.
July is the heart of summer. Expect the most consistent heat and the best chance for hot afternoons.
August cools off a touch but stays warm enough for festivals and patio dinners. Evenings get more comfortable, which is nice if humid nights aren’t your thing.
Notable Heatwaves and Extremes
Ottawa does get heatwaves from time to time. On some days, highs reach the mid-80s °F (29–30°C), and during rare extremes, the city has seen temperatures above 90°F (32°C).
Humidity makes these hot spells feel even warmer, especially in July when the air gets stagnant and dew points climb.
At night, even during heatwaves, Ottawa cools off more than southern Ontario cities. Lows rarely stay above 70°F (21°C), so you get a bit of relief.
Still, you might want to plan for the occasional stretch of uncomfortable heat, especially if you’re outdoors in the mid-afternoon.
Rainfall and Precipitation Patterns
Summer in Ottawa brings steady rainfall, plenty of wet days, and the odd thunderstorm. You’ll see measurable precipitation every month, with June usually being the wettest.
Short but intense storms are common, and they can shake up your outdoor plans or local travel.
Monthly Rainfall Totals
Rainfall in Ottawa during summer is pretty consistent, but June usually gets the most rain. On average, the city sees about 105 mm in June, making it the wettest month of the season.
July and August follow with slightly lower amounts, often between 80–90 mm each.
So, you’ll notice more rain at the start of summer, with a slow drop-off toward late August.
Unlike places with a sharp wet season, Ottawa’s rain stays spread out, so you get a mix of sunny and rainy days all summer.
| Month | Average Rainfall (mm) |
|---|---|
| June | ~105 mm |
| July | ~85 mm |
| August | ~80 mm |
These numbers cover both rainfall and quick summer showers that add up over time.
Frequency of Rainy Days
Each summer month in Ottawa brings a fair number of rainy days. June sees about 12–13 days with measurable precipitation, while July and August average 10–12 days each.
Rain usually comes as short showers, not all-day events. You might get rain in the afternoon but enjoy clear skies earlier.
Because of this, outdoor activities rarely get canceled outright, but it’s smart to stay flexible.
Light rain and scattered showers are common, yet heavy downpours do happen. Be ready for quick weather changes, especially in late afternoons when things can shift fast.
Thunderstorms and Heavy Rain Events
Thunderstorms show up regularly in Ottawa’s summer. They usually develop in the late afternoon or evening when warm, humid air mixes with cooler air.
These storms often bring quick but heavy rainfall, sometimes dumping over 20 mm in a short time.
You’ll also see lightning, gusty winds, and localized flooding, though the really severe stuff is less common than down south.
If you’re visiting, you’ll notice thunderstorms pass quickly. They might mess up your plans for an hour or two but rarely last all day.
Carrying a light rain jacket or umbrella is a good idea, so you’re not caught off guard.
Humidity and Sunshine During Summer
Ottawa summers bring warm temperatures, moderate humidity, and long daylight hours.
You’ll usually find conditions comfortable for most outdoor activities, with only the occasional day that feels heavy or damp.
Average Humidity Levels
Humidity in Ottawa during summer stays moderate compared to the rest of the year. Relative humidity averages between 55% and 65% from June through August.
July, being the warmest month, usually sees daytime highs near 27°C (80°F). Even then, humidity rarely hits extreme levels, so the heat feels less oppressive than in coastal or tropical places.
You might notice more humid days in late June and August after it rains. But Ottawa’s inland spot and steady breezes keep muggy weather from sticking around too long.
This makes summer here more comfortable than in a lot of other spots with similar temperatures.
Daily and Monthly Sunshine Hours
Summer in Ottawa means long daylight hours, so you get plenty of time for outdoor fun.
In June, daylight lasts close to 15.5 hours per day. By July, it’s about 14 hours, and by August, around 13.5 hours.
On average, you’ll get 8 to 9 hours of bright sunshine per day during summer. July is usually the sunniest, with lots of clear or partly cloudy days.
The combo of long days and frequent sunshine is great for sightseeing and festivals. Even when it rains, skies often clear fast, so you still squeeze in several hours of sun.
That’s just part of Ottawa’s continental climate and a big reason summer feels special here.
Cloud Cover and Sky Conditions
In Ottawa, summer skies shift from more frequent clouds in June to clearer conditions by August.
You’ll notice a drop in overcast days as the season goes on, which makes outdoor plans and just being outside a lot more enjoyable.
Clear Versus Cloudy Days
During summer, you get a mix of sunny and cloudy periods. Early in the season, skies are overcast or mostly cloudy about half the time.
By mid-August, that drops to about one-third of the time, so you get more chances for clear skies.
The clearest days pop up in early to mid-August. There’s about a 64% chance you’ll get clear, mostly clear, or partly cloudy skies on these days.
That’s perfect for walking along the Rideau Canal or hanging out in city parks.
Cloud cover usually falls into these categories:
- Clear (0–20%)
- Partly Cloudy (20–40%)
- Mostly Cloudy (40–60%)
- Overcast (60–100%)
By late summer, Ottawa leans toward the first two—clear and partly cloudy. So you can expect more days with good visibility and sunshine compared to earlier in the season.
Seasonal Variations in Cloudiness
Cloud cover in Ottawa shifts a lot during summer. In June, you’ll see more unsettled skies—about 51% of days end up mostly cloudy or just plain overcast.
But by late August, that number drops to around 37%. You really notice this seasonal shift, especially if you’re hoping for sunshine.
Usually, the clearest point of the season lands right around August 10. Nearly two-thirds of the day can be clear or just partly cloudy.
This change matches up with slightly shorter days, but you get more consistent sky clarity.
If you’re planning a trip, keep in mind that June can swing back and forth. July and August, though, lean toward steadier, clearer skies.
Love being outside, taking photos, or just soaking up the city? Late July into August is your best bet for bright, wide-open views of Ottawa’s landmarks and waterways.
Wind, Air Quality, and Other Weather Factors
Ottawa’s summer brings steady winds, moderate humidity, and usually pretty good air quality. These things really shape how comfortable you’ll feel outside and how you plan your time in the city.
Prevailing Wind Patterns
During summer, you can expect light to moderate winds in Ottawa. Average wind speeds usually sit between 7 to 12 mph (11 to 19 km/h). That’s enough to give you a bit of relief on hot days, but not enough to mess up your plans.
The Ottawa Macdonald-Cartier International Airport often records winds coming from the west and southwest. That’s pretty typical for southern Ontario, and it brings in drier, warmer air.
Sometimes, breezes shift from the north or east, and that can cool things down a little.
Wind really does make a difference in how the air feels. Even on those muggy days, a steady breeze can keep things from feeling too heavy.
If you’re out cycling or walking along the Rideau Canal, you’ll probably find it easier to enjoy yourself when there’s a bit of wind.
Of course, calm periods happen, especially in the evenings. Winds can drop below 5 mph (8 km/h), and suddenly you notice the humidity a lot more because the air just sits there.
Air Quality in Summer
Air quality in Ottawa during summer usually falls somewhere between good to moderate on the Air Quality Health Index. Most days, you can head outside and not worry too much about it.
Ozone levels on hot afternoons and fine particulate matter from regional sources play the biggest roles here. Sometimes, smoke from wildfires elsewhere in Canada drifts in, making the sky hazy and cutting down visibility.
You might notice a bit more pollution near busy roads or right downtown. In contrast, suburban and rural areas tend to feel a bit fresher.
Stations at the airport and around the city usually show air quality that’s safe for most healthy people.
If you’re sensitive to air quality or have asthma, it’s a good idea to check the daily forecast. Local agencies share updates so you can plan outdoor exercise or travel and hopefully avoid discomfort.