Holidaymakers on the beach at Arcachon, south-west France, earlier this month

Almost half of France was on heatwave high alert on Saturday, as 470 kilometres of traffic jams clogged the country's motorways and Paris took emergency measures to fight soaring pollution.

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With temperatures expected to reach 32-38°C for the fifth day running Saturday, 43 of mainland France's 95 départements were on orange heatwave alert, the second highest level, and most of the rest of the country was on the next level.

But official weather-watcher Méteo France forecast storms north of Paris and some clouds on the Mediterranean coast, where for once temperatures are lower than Paris, Burgundy, Champagne and the centre, and in the Jura and Alps mountains.

Temperatures were expected to be relatively low, around 22-24°C at their highest, on the Channel coast.

The heatwave, set to continue on Sunday and on Monday in some areas, has been caused by a high-altitude anticyclone, which is preventing fresh air coming from the Atlantic Ocean and spreads from Morocco to Germany.

Traffic jams clog roads

Although few traffic jams were reported at 10.00am, traffic monitor Boison Futé recorded 470 kilometres of tailbacks on major French roads at midday on a weekend that is the end of summer holidays for thousands of families.

The A7, A10 and A63 motorways were worst affected.

Motorway operator Vinci Autoroute advised motorists to ventilate their vehicle well and stop more often than usual.

Paris extends anti-pollution measures

Paris's city council on Friday asked officials to limit heavy goods vehicles travelling through the Ile de France region and lower speed limits in an attempt to reduce pollution, which has soared over the last four days.

The city's bike- and car-sharing schemes have been made free of charge and health warnings broadcast in the metro and on municipal advertising hoardings, as well as on public broadcasters nationwide.

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