Millions in Canada swelter as heatwave continues to move east

Another record-breaking heatwave has hit parts of Canada and the US, bringing extreme temperatures and poor air quality.

Extreme heat warnings have been in place across multiple Canadian provinces, including most of Ontario and part of Quebec, Manitoba and the Northwest Territories - affecting millions of people.

The high temperatures are expected to continue for Canada, as well as for parts of the US Midwest and Northeast, into Wednesday as the strong area of high pressure moves eastwards.

It has already led to all-time temperature records being broken in parts of Montana and Utah, and comes after a record-breaking heatwave hit large portions of the US earlier this month.

The Canadian city of Toronto was braced for possible record-breaking heat on Tuesday, but stopped short at 98F (36C).

Commuter trains were running on delays due to "weather related track conditions", according to the regional public transit service, while Environment Canada warned that hot and humid air could result in deteriorating air quality.

Central and eastern areas of Canada have also been hot, but a cold front is set to bring lower temperatures over the next few days. It will also bring the threat of severe thunderstorms, which could also affect parts of New England in the US.

Those thundery conditions will develop more widely across the east of North America by the weekend, pushing away the worst of the heat - although temperatures in many areas will remain above the seasonal norm.

Meanwhile, millions of people are under heat advisories in the US cities of Boston, New York City, Philadelphia and as far west as Buffalo, New York, that will last through Wednesday.

The northern Plains, Midwest and Northeast will bear the brunt, with temperatures in Chicago forecast to reach 97F on Wednesday.

New York could reach 100F, while Washington DC is expecting 102F. A few places could get even hotter, with high humidity expected to make it feel even more uncomfortable.

Earlier this week, the city of Billings in Montana reached 111F, where its previous heat record was 108F. In Utah's Salt Lake City, the previous record of 107F was broken when it reached 109F.

The high temperatures come not long after a record-breaking 4 July heatwave hit large portions of the US.

More than 165 million people sweltered under record temperatures along the US East Coast and Midwest, and at least 44 deaths were reported.

The heat also disrupted Fourth of July celebrations, including the Washington DC parade, which was cancelled.

Heatwaves have become more frequent, more intense and longer-lasting because of human-induced climate change. The world has already warmed by about 1.1C since the industrial era began and temperatures will keep rising unless governments around the world make steep cuts to emissions.