USA & Canada Weather: 43°C Texas Heat, Storms and a Late-August Warm-Up
The next ten days will divide the United States and Canada into several very different weather zones.
USA & Canada weather 17–26 August: key points
- Dallas: the standout heat hotspot, with repeated 40–43°C days and very warm nights near 28–31°C.
- Atlanta: extreme heat near 38°C early, followed by thunderstorms and partial relief.
- Denver and Los Angeles: heat builds later in the period, reaching roughly 37–38°C.
- New York and Chicago: large temperature swings, rain episodes and another warm-up near 24–26 August.
- Canada: generally milder, with cooler nights and occasional rain; Calgary has the strongest late-period rain/wind signal.
- Forecast uncertainty: days 8–10 should be treated as a trend, especially for rainfall timing and exact maxima.
The strongest and most persistent heat will remain across the southern and south-central United States. Dallas stands out as the major heat hotspot, with temperatures repeatedly above 40°C and potentially approaching 43°C. Atlanta also begins the period under intense heat, while Denver and Los Angeles become increasingly hot later in the forecast.
The Pacific Northwest will be almost the opposite. Seattle and Vancouver remain mostly dry and comfortable, with daytime temperatures generally in the 20s. Across eastern Canada, Toronto, Montreal and Ottawa will experience a much milder pattern, with several cooler intervals and only short-lived warmer spells.
The eastern United States will be more changeable. New York City gets a warm start, rain, a cooler weekend and then another rebound toward 30°C. Miami stays hot and humid throughout, but rainfall becomes increasingly important during the second half of the period.
So the main ten-day story is clear:
extreme heat in Texas and parts of the southern U.S., increasing heat in the West and Rockies, milder conditions across much of Canada, and several sharp temperature swings around the Great Lakes and Northeast.
Let’s look at the forecast city by city.
New York City: Warm Start, Rain, Cooler Weekend, Then Heat Returns
New York City starts the period with unsettled weather.
Monday, August 17, reaches around 27–28°C, but Open-Meteo indicates approximately 15 mm of rain, making this one of the wettest days of the ten-day forecast for the city.
The weather then turns hotter.
Tuesday reaches close to 30°C, followed by around 31°C on Wednesday, August 19.
Wednesday currently looks like the warmest day of the first half of the forecast, with a very mild nighttime temperature close to 24°C.
But that warmth does not last.
By Saturday and Sunday, August 22–23, highs drop to only around 23°C. Some rain also returns, with approximately 4–7 mm possible during the weekend.
And then comes another reversal.
Monday, August 24, rebounds to around 29°C, while Wednesday, August 26, may reach approximately 31°C again.
Rain could also return on August 26, with around 7–8 mm currently indicated.
So New York gets a classic late-summer temperature roller coaster:
rain → 31°C heat → 23°C cool spell → another return toward 30°C.
Miami, Florida: Hot, Humid and Increasingly Wet
Miami remains firmly locked in tropical summer weather throughout the period.
Daytime temperatures stay between approximately 30 and 34°C, with the highest readings during the first few days.
Tuesday, August 18, may reach around 34°C.
But daytime heat is only part of the story.
Nighttime temperatures become extremely warm, frequently remaining around 29°C during the second half of the forecast.
That means very little overnight relief from the heat and humidity.
The first several days are relatively dry, but rainfall chances increase from around August 21 onward.
The more notable rainfall signals currently include:
- around 8 mm on August 23
- approximately 11 mm on August 25
- around 7 mm on August 26
This does not necessarily mean all-day rain. In Miami, these totals may come from tropical showers and thunderstorms concentrated into relatively short periods.
The main concern therefore remains the combination of:
heat + humidity + very warm nights + increasing thunderstorm potential.
Atlanta, Georgia: Extreme Heat First, Stormier and Cooler Later
Atlanta begins the ten-day period under some of the strongest heat in the eastern United States.
Monday reaches approximately 37°C.
Tuesday, Wednesday and Thursday may all reach around 38°C.
The current Open-Meteo peak is approximately 38.1°C.
Nighttime temperatures also remain extremely high, with lows around 25–27°C.
This creates significant cumulative heat stress because the city receives very little overnight cooling.
But there is an important change around August 21.
Temperatures fall from around 38°C Thursday to approximately 33°C Friday, while rainfall increases.
Current rainfall totals are roughly:
- 5–6 mm Friday
- around 3 mm Saturday
- another 3 mm Sunday
Sunday may be the coolest day of the ten-day period, at around 31°C.
After that, the heat begins rebuilding.
By August 25–26, temperatures return toward approximately 35–36°C.
So Atlanta’s ten-day pattern can be summarized as:
extreme heat → thunderstorms and partial relief → another late-period warm-up.
Chicago, Illinois: Cool Start, Midweek Rain and a Strong Warm-Up at the End
Chicago will be one of the more variable major U.S. cities.
Monday starts surprisingly cool at only around 23°C.
Tuesday warms rapidly to approximately 29°C.
Wednesday then turns wetter, with around 6 mm of rain currently forecast and a maximum near 25°C.
Most of the middle of the forecast remains comfortable, generally between 23 and 28°C.
The coolest day could be Monday, August 24, at only around 22°C.
But look at what happens next.
Tuesday jumps to nearly 30°C, and Wednesday, August 26, could reach around 31°C.
Winds also become stronger late in the forecast, with gusts potentially exceeding 50 km/h on August 26.
So Chicago ends the ten-day period very differently from how it begins.
Dallas, Texas: The Most Dangerous Heat Hotspot
Dallas is the standout extreme-heat location in this forecast.
This is not simply a few hot afternoons.
Open-Meteo currently shows a persistent sequence near or above 40°C.
Monday, August 17:
around 41°C
Tuesday:
approximately 43°C
Wednesday:
around 42°C
Thursday:
around 42°C
The current forecast peak is approximately:
42.9°C on August 18.
Even after a slight reduction Friday, temperatures remain around 39°C.
Then the heat intensifies again:
Saturday around 42°C
Sunday around 42°C
Monday around 41°C
and temperatures remain close to 40°C through August 26.
There is another major problem — nighttime heat.
Minimum temperatures frequently stay around 28–31°C.
That means homes, buildings, roads and the human body receive almost no meaningful overnight cooling.
And there is currently virtually no rainfall signal for the entire ten-day period.
Dallas therefore has the highest heat-health concern among the cities in this forecast.
The combination is dangerous:
40–43°C afternoons + near-30°C nights + dry conditions lasting many days.
Denver, Colorado: Strong Heat Builds Over the Rockies
Denver also faces significant heat.
Monday already reaches approximately 34°C.
Tuesday rises to around 35°C.
Most of the period remains above 32°C.
The hottest part arrives later.
Saturday, August 22, could reach around 37.5°C.
Monday, August 24, may again approach 37°C.
That is significant heat for Denver’s elevation.
Rainfall remains limited overall. Only small daily totals appear in the model, generally below 2 mm.
This means the dominant weather story is not thunderstorms but persistent hot and mostly dry conditions.
Nights also become progressively warmer, rising from around 15°C early in the period to 22–24°C later.
Los Angeles, California: A Significant Heat Build-Up
Los Angeles starts warm but becomes significantly hotter during the second half of the forecast.
Monday reaches approximately 31°C.
Tuesday and Wednesday rise into the 34–35°C range.
Thursday approaches 36°C.
After remaining near 34–35°C for another couple of days, another pulse of heat arrives.
Sunday and Monday, August 23–24, both reach approximately 37°C in the current Open-Meteo run.
The nighttime trend is particularly striking.
Minimum temperatures rise from around 18°C Monday to 25–28°C later in the period.
Monday, August 24, could remain near 28°C overnight in the model grid point.
The entire ten-day period is essentially dry.
This creates a growing heat and fire-weather concern, particularly away from the immediate coast and in hotter inland parts of the Los Angeles metropolitan area.
Seattle, Washington: Warm, Dry and Remarkably Stable
Seattle will be one of the calmest locations in this forecast.
There is currently no measurable rain forecast for the entire ten-day period.
Monday reaches around 26°C.
Tuesday and Wednesday approach 29°C.
Friday may become the warmest day, at around 29–30°C.
Temperatures cool temporarily during the weekend to around 25°C, before climbing back toward 29°C Monday and Tuesday.
Nights remain comfortable, generally around 13–16°C.
Compared with the extreme heat affecting Texas, Georgia and parts of the Southwest, Seattle’s weather will feel almost ideal:
warm afternoons, cool nights and very little weather disruption.
Toronto: Mild, Mostly Dry and No Major Heatwave
Toronto experiences a much gentler pattern than many U.S. cities.
Monday and Tuesday both reach approximately 26°C.
Wednesday stays similar, near 26°C, with a small chance of rain.
Thursday falls to around 24°C, followed by the coolest day on Friday at only about 22°C.
Temperatures rebound during the weekend.
Saturday reaches approximately 26°C and Sunday around 27°C, currently the warmest day of the ten-day period.
Monday then cools back toward 23°C.
Most of the period is dry.
The main rain signal comes at the very end of the forecast, when approximately 10 mm may fall on August 26.
Overall, Toronto avoids both extreme heat and prolonged rain.
Montreal: Coolest of the Major Eastern Cities
Montreal remains noticeably cooler than Toronto and New York.
Monday reaches only around 21°C, accompanied by approximately 7 mm of rain.
Tuesday improves to around 24°C.
The rest of the week generally stays between approximately 21 and 26°C.
The warmest day may be Saturday, August 22, near 26°C.
Another wetter period appears around Sunday, August 23, with approximately 6 mm of rain.
Night temperatures become quite fresh.
Friday morning may fall to around 13°C, with other nights in the 13–17°C range.
Montreal therefore gets a very typical late-summer pattern:
mild days, cool nights and occasional frontal rain.
Ottawa: Comfortable Days and Cool Nights
Ottawa also avoids major heat.
Monday reaches around 24°C.
Tuesday rises to approximately 26°C.
Thursday cools to around 22°C.
Saturday provides another warmer interval near 27°C, which is currently the highest forecast temperature.
But the nighttime temperatures tell an interesting story.
Friday morning could fall to approximately 10°C.
Several other nights remain around 11–14°C.
Rainfall is generally light and scattered.
The largest current signal is around 4 mm on August 26.
So Ottawa’s period is best described as comfortable late-summer weather with some distinctly cool mornings.
Calgary: Warm Spells, Sharp Swings and a Wet Sunday
Calgary will be considerably more variable.
Monday starts around 24°C.
Tuesday warms toward 28°C, and Wednesday reaches approximately 29°C.
Thursday then drops back toward 23°C.
But another stronger warm-up follows.
Friday reaches around 28°C.
Saturday climbs to approximately 31°C.
Then comes the most interesting weather change.
Sunday, August 23, falls to around 27°C, with approximately 12 mm of rain and wind gusts potentially above 50 km/h.
That currently makes August 23 one of the more notable Canadian weather days in this outlook.
Temperatures recover again later, potentially returning to around 31°C on August 26.
Vancouver: Mild Pacific Weather With Very Little Rain
Vancouver remains mild throughout the period.
Monday reaches around 25°C.
Tuesday drops to approximately 22°C.
Wednesday only reaches around 21°C.
A warmer period returns Thursday near 24°C, followed by temperatures in the low 20s.
Saturday may be the coolest day, near 19°C, before the city warms again to approximately 26°C on August 24.
Rainfall remains extremely limited.
Only a small amount is currently indicated around August 21–22.
For late August, this is a remarkably calm Pacific pattern.
# USA & Canada 10-Day Weather Trend: What Matters Most?
The most important feature of the August 17–26 forecast is the enormous temperature contrast across North America.
At one extreme:
Dallas may reach 42–43°C.
At the other:
Montreal, Vancouver and parts of the Great Lakes region periodically struggle to reach even 20–23°C.
That means the continental temperature difference between major cities may exceed 20°C on some days.
Hottest locations
Dallas: up to 42.9°C
Atlanta: up to 38.1°C
Denver: up to 37.5°C
Los Angeles: up to 36.8°C
Miami: around 34°C, but with much higher humidity
Most persistent heat
Dallas is clearly number one.
The model currently keeps the city close to or above 40°C during almost the entire ten-day period, with virtually no rainfall and extremely warm nights.
Los Angeles and Denver also show persistent heating, especially from August 20 onward.
Wetter locations
The heaviest individual rainfall signals among the selected cities currently include:
New York City: around 15 mm on August 17
Calgary: around 12 mm on August 23
Miami: around 11 mm on August 25
Toronto: around 10 mm on August 26
Montreal: around 7 mm on August 17
Rainfall forecasts beyond about a week have substantially greater uncertainty, so the exact totals for August 24–26 should be treated as a trend rather than a precise prediction.
Coolest pattern
Canada remains mostly comfortable.
Montreal and Ottawa frequently stay in the low-to-mid 20s, while Vancouver remains around 19–25°C.
Chicago also experiences a surprisingly cool period around August 23–24 before warming sharply again.
Main forecast message
The southern United States stays locked beneath intense late-summer heat, while much of Canada remains comparatively mild.
The most serious weather concern is prolonged extreme heat in Texas, followed by significant heat in Atlanta, Denver and Los Angeles.
Meanwhile, frontal systems bring periodic rain and large temperature changes across the Northeast, Great Lakes and eastern Canada.
And there is one more thing to watch.
By August 24–26, several cities begin another significant warm-up — including New York, Chicago, Denver and Calgary. Whether this develops into a broader late-August heat expansion across North America will become much clearer in the next forecast update.
Forecast period: August 17–26, 2026
Data source: Open-Meteo Forecast API
Cities analyzed: New York City, Miami, Chicago, Dallas, Los Angeles, Denver, Atlanta, Seattle, Toronto, Montreal, Ottawa, Calgary and Vancouver.
Forecast confidence is highest during the first 5–7 days. Details near days 8–10, especially rainfall timing and exact maximum temperatures, can still change.
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USA & Canada weather FAQ: 17–26 August 2026
Where will the most dangerous heat be?
Dallas is the standout heat hotspot, with the forecast showing repeated 40–43°C afternoons and nighttime temperatures often near 28–31°C.
Which U.S. cities warm up again late in the forecast?
New York, Chicago, Denver and Calgary all show another meaningful warm-up around August 24–26.
Where are the largest rainfall signals?
The supplied forecast highlights about 15 mm in New York on August 17, around 12 mm in Calgary on August 23, around 11 mm in Miami on August 25 and around 10 mm in Toronto on August 26.
Which Canadian cities stay coolest?
Montreal, Ottawa and Vancouver generally remain in the low-to-mid 20s for much of the period, with several notably cool nights.
How reliable are days 8–10?
Confidence is lower near August 24–26, especially for rainfall timing and exact maximum temperatures. Those later values should be treated more as a trend than as a precise day-by-day prediction.
