USA & Canada Weather Forecast August 22–31, 2026: 114°F Heat, Flooding Rain and a Dramatic Late-Summer Split

Late August will look like three different seasons across North America at the same time.

The Desert Southwest and Texas remain trapped in dangerous heat, with Phoenix approaching 114°F (46°C) and Dallas around 110°F (43°C).

At almost the same time, a much wetter pattern develops farther east. Open-Meteo currently gives New York City close to 1.9 inches (49 mm) of rain on August 27, while Toronto could receive around 1.8 inches (45 mm) on August 23.

And then there is Canada.

Calgary could climb above 91°F (33°C) before falling into the upper 60s°F just two days later. Toronto drops into the mid-60s°F before returning near 80°F at the end of the month. Winnipeg has a late-month model signal for almost 1.7 inches (43 mm) of rain in one day.

This is not a simple transition from summer to fall.

Instead, the final ten days of August look increasingly divided between extreme southern heat, tropical thunderstorms, heavy-rain corridors and abrupt early-fall-like cool shots across parts of Canada and the northern United States.

The forecast below covers August 22–31, 2026, using daily Open-Meteo Forecast API data for major U.S. and Canadian cities with high weather and travel search interest.

USA & Canada weather forecast at a glance

These are numerical model forecasts, not official watches or warnings. Thunderstorm rainfall, hail and wind can change substantially as individual systems approach.

Phoenix weather: the most extreme heat in the forecast

Phoenix is the clear heat leader.

Open-Meteo gives the city approximately 114°F (45.8°C) on August 22, followed by another stretch mostly between 107°F and 113°F (42–45°C) through the end of August.

But the daytime heat is only half the story.

Some overnight minimums are extraordinarily high. The model has nighttime temperatures reaching roughly 99°F (37°C) around August 26.

That would provide almost no meaningful overnight relief.

Rain is essentially absent, apart from a trace signal on August 24.

For Phoenix, there is currently no real late-summer break in this forecast period.

Dallas: 110°F heat before a temporary break

Dallas is also facing an exceptional heat signal.

Temperatures climb from around 107°F (42°C) on August 22 to approximately:

• 109°F (43°C) on August 23
• 110°F (43°C) on August 24
• around 109°F (43°C) again August 25–26

Nighttime heat may be nearly as significant, with a minimum close to 90°F (32°C) on August 24.

A temporary break arrives around August 27, when the daytime high drops to roughly 98°F (37°C) and about 0.17 inch (4 mm) of rainfall appears.

But this is not the end of the heat.

Dallas rebounds toward 104°F (40°C) by August 31.

Houston: 104°F, then a notable late-week cooldown

Houston follows a similar pattern, though the break is more noticeable.

Highs rise to approximately:

• 100°F (38°C) Aug 22
• 102°F (39°C) Aug 24
• 103°F (40°C) Aug 25
• 104°F (40°C) Aug 26

Then temperatures fall sharply to around 91°F (33°C) on August 28.

That is a drop of roughly 13°F (7°C) from the peak.

Scattered rain returns around August 29–30, though the current city-grid totals remain relatively modest.

Los Angeles: nearly 100°F and essentially no rain

Los Angeles remains remarkably hot and dry.

Highs mostly stay in the mid-to-upper 90s°F, reaching approximately 99°F (37°C) on August 29.

Open-Meteo currently gives zero measurable precipitation for the entire August 22–31 period.

Even more unusual is the nighttime pattern. Several late-August minimum temperatures are modeled in the upper 70s°F, and locally around 80°F (27°C).

This is a persistent heat signal rather than a short two-day spike.

Denver: heat, thunderstorms, then almost 100°F again

Denver has a very different late-August pattern.

The city starts close to 98°F (37°C) on August 22.

Temperatures gradually ease before a much wetter day appears on August 26, when Open-Meteo gives around 0.57 inch (14.6 mm) of precipitation.

That could include locally heavier convective rainfall, especially given Denver’s summer thunderstorm climatology.

But after the rain, heat rebuilds.

By August 31 the model pushes Denver back to around 100°F (37.5°C).

So the rain episode looks more like a temporary interruption than the arrival of fall.

Miami: thunderstorms become the main story

Miami does not show the extreme daytime heat of Texas or Arizona, but humidity and thunderstorms dominate the forecast.

Highs remain around 88–91°F (31–33°C) almost every day.

The wettest signal is currently August 23 with about 0.52 inch (13 mm) of rain.

August 24 carries a model weather code consistent with a thunderstorm with hail potential, and additional thunderstorm signals appear later in the week.

This does not mean hail is guaranteed in Miami. The WMO code is a model-derived weather classification, not a National Weather Service warning.

But the repeated thunderstorm codes clearly indicate a very unstable tropical air mass.

Atlanta: a 15°F drop, thunderstorms, then heat returns

Atlanta has one of the sharper temperature swings in the eastern United States.

The city stays around 92–93°F (33–34°C) through August 25.

Then thunderstorms increase.

August 26 has around 0.17 inch (4.4 mm) of rain, followed by roughly 0.34 inch (8.7 mm) on August 27.

The temperature on August 27 drops to only about 79°F (26°C).

That is roughly 15°F cooler than the hottest part of the forecast.

But summer quickly returns.

By August 30 Atlanta is back near 94°F (34°C).

New York City: nearly 2 inches of rain in one day

New York has one of the strongest rainfall signals in the entire U.S. forecast.

The first several days are relatively quiet, with highs mostly in the upper 70s and lower 80s°F.

Then the pattern becomes much wetter.

On August 27, Open-Meteo currently gives around:

1.91 inches of rain — approximately 49 mm.

The WMO weather code is also consistent with intense rain showers.

That amount would be enough to create urban flooding concerns if a large portion falls within only a few hours.

However, this is still a model forecast several days in advance, not a confirmed flash-flood warning.

Temperatures rise again to about 86°F (30°C) on August 28 before easing late in the month.

Chicago: highly changeable with a late thunderstorm signal

Chicago stays relatively moderate compared with the southern United States.

Highs generally remain in the mid-70s to mid-80s°F.

The warmest day is currently around 86°F (30°C) on August 26.

Then temperatures fall to approximately 73°F (23°C) on August 27.

By August 31, the forecast again reaches around 85°F (29°C), but this time accompanied by a thunderstorm weather code and gusts around 34 mph (55 km/h).

That final-day signal deserves monitoring as the forecast window shortens.

Seattle: 89°F heat followed by a 23°F temperature crash

Seattle may produce one of the largest temperature swings in the forecast.

August 25 reaches approximately 89°F (32°C).

The city then steadily cools:

around 84°F Aug 26,

80°F Aug 27,

71°F Aug 29,

and only 66°F (19°C) on August 31.

That is a drop of about 23°F (13°C) from the peak.

Rainfall remains very light, so this is primarily a temperature transition rather than a major storm.

For Seattle, the end of August looks much more like an early-fall air mass.

Toronto: two days of very heavy rain

Toronto is currently the standout rainfall hotspot in Canada.

Open-Meteo gives approximately:

0.95 inch (24 mm) on August 22, followed by

1.77 inches (45 mm) on August 23.

That is nearly 2.7 inches (69 mm) in two days at the city grid point.

The August 23 weather code is consistent with very heavy showers.

Temperatures also fall sharply, reaching only around 64°F (18°C) on August 24.

Late August then becomes warmer again, eventually reaching around 80°F (27°C) on August 31.

Toronto therefore gets a very clear sequence:

heavy rain → early-fall chill → late-summer rebound.

Montreal: increasingly unsettled, then a cool late-month break

Montreal starts warm, close to 79°F (26°C) on August 22.

Rain becomes more frequent after that.

Open-Meteo gives about:

• 0.13 in (3 mm) Aug 23
• 0.43 in (11 mm) Aug 24
• 0.28 in (7 mm) Aug 25
• 0.24 in (6 mm) Aug 27
• 0.28 in (7 mm) Aug 28

Gusts could reach approximately 33 mph (53 km/h) around August 28.

Then temperatures fall to just 64°F (18°C) on August 29.

But even here, the cool weather is not permanent: Montreal rebounds to almost 80°F (27°C) on August 31.

Ottawa: September-like mornings before a rapid warm-up

Ottawa shows a similar but even sharper early-fall signal.

The daytime high drops to around 64°F (18°C) on August 29.

The nighttime minimum falls to approximately 48°F (9°C).

That is one of the clearest genuinely cool late-August mornings among the major cities analyzed.

Yet by August 31, the daytime temperature rebounds to around 80°F (27°C).

So eastern Canada is not entering permanent fall — it is experiencing a strong but temporary cool shot.

Vancouver: more than an inch of rain, then cooler weather

Vancouver has a major rainfall signal very early in the period.

On August 23, Open-Meteo gives around 1.22 inches (31 mm) of rain.

Afterward the weather briefly improves, and August 25 warms to around 78°F (26°C).

Then the Pacific pattern turns cooler again.

By August 29 the daytime high is only about 64°F (18°C), with another smaller rain episode.

Vancouver therefore shifts toward an unmistakably more autumn-like pattern well before inland western Canada does.

Calgary: 91°F heat followed by a 22°F collapse

Calgary may see one of Canada’s most dramatic thermal swings.

Temperatures rise to around 84°F (29°C) on August 26, then peak near:

91°F (33°C) on August 27.

Only two days later, the high falls to approximately:

69°F (20°C) on August 29.

That is a roughly 22°F (13°C) drop in two days.

August 23 also has gusts near 36 mph (59 km/h).

So Calgary may experience both summer heat and an early-fall transition within the same week.

Winnipeg: almost 1.7 inches of rain on August 30

Winnipeg is another Canadian city with a significant late-August rainfall signal.

Temperatures reach around 86°F (30°C) on August 24, then fall to approximately 71°F the following day.

The more important feature comes at the end of the month.

Open-Meteo currently gives approximately:

1.69 inches (43 mm) of rain on August 30.

The weather code is consistent with intense showers.

Given the lead time, the exact total is uncertain, but the signal is strong enough to make Winnipeg one of the primary Canadian cities to monitor late in August.

The biggest U.S. and Canada weather anomalies before September

The first and most obvious anomaly is extreme Southwest heat.

Phoenix remains around 110–114°F for much of the period, with astonishingly warm nights.

The second is the Texas heat dome. Dallas reaches roughly 110°F, Houston about 104°F, and both cities retain very warm nights.

The third is the heavy-rain corridor in the Northeast and eastern Canada.

New York has a model signal near 2 inches in one day, Toronto around 1.8 inches, and Montreal receives several separate rain events.

The fourth is the Canadian temperature roller coaster.

Calgary moves from 91°F to 69°F in about two days. Ottawa and Montreal fall to around 64°F before rebounding close to 80°F. Toronto experiences a similar pattern.

And the fifth anomaly is the Pacific Northwest split.

Seattle briefly reaches nearly 90°F, then falls to the mid-60s°F by August 31.

Where will North America be hottest?

Among the cities analyzed:

Phoenix — around 114°F (46°C)

Dallas — around 110°F (43°C)

Houston — around 104°F (40°C)

Denver — near 100°F (38°C)

Los Angeles — near 99°F (37°C)

The highest heat risk remains concentrated in the Desert Southwest, Texas and parts of the interior West.

Where is the highest rain risk?

The largest city-scale daily rainfall signals are currently:

New York City — 1.91 in (49 mm), Aug 27

Toronto — 1.77 in (45 mm), Aug 23

Winnipeg — 1.69 in (43 mm), Aug 30

Vancouver — 1.22 in (31 mm), Aug 23

Denver — 0.57 in (15 mm), Aug 26

Miami — 0.52 in (13 mm), Aug 23

Montreal — 0.43 in (11 mm), Aug 24

The exact amounts will likely change as these events approach. For thunderstorm rainfall, timing and hourly intensity matter more than the precise 10-day city-grid total.

USA & Canada weather forecast: the bottom line

The final ten days of August 2026 will not behave like a smooth transition toward fall.

In the Southwest and Texas, summer remains extreme.

Phoenix could remain above 110°F for multiple days, Dallas approaches 110°F, and Houston reaches around 104°F.

Farther east, moisture becomes increasingly important. Miami remains stormy, Atlanta sees a thunderstorm-driven cool break, and New York develops one of the strongest heavy-rain signals of the period.

Canada looks dramatically more variable.

Toronto begins with potentially very heavy rain and then briefly turns cool. Calgary moves from 91°F to the upper 60s°F in only two days. Vancouver becomes wetter and more autumn-like, while Montreal and Ottawa experience cool late-August days before temperatures rebound.

So September may be approaching, but North America is entering it from completely different directions.

Arizona and Texas will still feel like midsummer.

Seattle and Vancouver may briefly feel like October.

And across eastern Canada, late August could deliver both heavy rain and the first convincing taste of early fall — before summer tries to return one more time.

USA & Canada weather forecast FAQ

Will the U.S. have another major heatwave before September?

Yes. The strongest heat is concentrated in Arizona, Texas and parts of the West. Phoenix may reach around 114°F, Dallas close to 110°F and Houston around 104°F.

Where is the heaviest rain expected?

The strongest current city-scale model signals are New York City, Toronto, Winnipeg and Vancouver.

Will Toronto cool down before September?

Yes. Toronto may fall to around 64°F on August 24 after heavy rain, but temperatures could rebound to around 80°F by August 31.

Is fall arriving early in Canada?

Only temporarily in some regions. Vancouver, Calgary, Ottawa, Montreal and Toronto all show cool episodes, but several cities warm sharply again before the end of August.

Will Phoenix cool down?

Not significantly during this forecast period. Highs remain mostly above 107°F, with several days near or above 110°F.

Are these official severe-weather warnings?

No. These are numerical weather-model forecasts. For hurricanes, tornadoes, flash floods, severe thunderstorms and heat emergencies, official alerts from NWS/NOAA in the U.S. and Environment and Climate Change Canada should take priority.

Super El-Nino 2026