Much of India has been reeling under a sweltering heat wave that has claimed more than 100 lives as temperatures rose to 46C last week. Water shortages and powercuts made life even more unbearable as the monsoon stalled in its progress northwards. But on Tuesday morning, Delhi and much of the north woke up to enjoy showers of cool rain as the monsoon suddenly accelerated and covered about 500km overnight.

Meteorologists warn, though, that apart from the delay in the monsoon’s progress, there could be a shortfall in this year’s rainfall.

Exactly why the monsoon has stuttered is not certain, but one clue may come from the Pacific. Australian meteorologists are now fairly sure that an El Niño is developing in the tropical seas of the Pacific. El Niños recur every few years and the first sign is usually when the seas off the coast of South America warm up and set off drenching downpours in Chile and Peru. But the effects of an El Niño can ripple out across the world, such as droughts in Australia, Indonesia and the Philippines, a reduced monsoon in India, floods in Kenya and torrents of rain in Central Europe. However, the power of each El Niño varies considerably, and it is not known how severe the coming El Niño will be, nor what its likely impacts will be.

Much of the UK roasted last week as temperature hit 30C or more and prompted official warnings about taking care in the heat. But storms and flashfloods lashed western and northern areas of the British Isles, and on Thursday Dublin suffered floods as Atlantic air streamed in from the west. Cooler, wetter weather is now sweeping across the whole UK — just in time for the weekend.