Extreme weather: heat strains healthcare systems, says WHO; Nasa to meet climate experts – as it happened

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• Phoenix sees no let-up in extreme temperatures
• Italy strike threat as Greek workers struggle with heat

Here are some more images from the wires of the wildfires that swept through forestland and towns north-west of Athens for a second day. The fires forced the evacuation of more than 1,000 children close to a Greek seaside resort.

Tourists flocked to China's scenic Flaming Mountains to experience searing high temperatures amid punishing heatwaves that have scorched much of the northern hemisphere.