Temperatures reached new highs on Monday as heatwaves and wildfires scorched swathes of the Northern Hemisphere, forcing the evacuation of 1,200 children close to a Greek seaside resort.Health authorities have sounded alarms from North America to Europe and Asia, urging people to stay hydrated and shelter from the burning sun, in a stark reminder of the effects of global warming.Near Athens, a forest fire flared in strong winds by the popular beach town of Loutraki where the mayor said holiday camps for youngsters had come under threat.