Unseasonally wet weather struck southern Pakistan and north-west India on Wednesday, as heavy rain rolled in from the west, accompanied by thunderstorms, hail, and strong winds.

Karachi, Pakistan’s largest city, was particularly badly affected, locally recording more than 50mm of rain with winds gusting up to 60mph. Walls, buildings, and a pedestrian bridge collapsed, with flooding and power outages across the city. At least 18 people were killed and several more injured, many by structural collapses, with other deaths attributed to a fallen tree and a lightning strike.

Storms were less intense for the neighbouring Indian provinces of Gujarat and Rajasthan, with most areas receiving no more than 15mm, though the city of Rajkot recorded 38mm. Disruption was still felt, however, with some power outages alongside minor damage to trees and buildings. Of greater concern is the impact on local agriculture, with farmers raising concerns of crop damage and disruption to impending harvests.

Heavy rain is rare in the region at this time of year; the majority of annual rainfall occurs during the monsoon between June and September. The average March rainfall in Karachi is 15.7mm, and the month is usually one of the driest in north-west India: most of Gujarat usually has less than 1mm on average and large parts of Rajasthan no more than 5mm.

Meanwhile, large parts of the western US have been hit by a heatwave that intensified through this week, with temperatures expected to peak on Friday and Saturday. This heatwave has been caused by a meandering jet stream and an almost stationary area of high pressure. These two atmospheric anomalies caused a warm flow of air from the south to become trapped, and with clear skies, the air becomes increasingly hot as it is heated by the sun. This effect is also referred to as a heat dome.

Maximum temperatures will widely exceed 30C across the south-west, about 10-15C above the seasonal average. Thursday saw temperatures soar to 42.2C in Indio, California, with many individual stations seeing March records broken as well.

Phoenix, Arizona is expected to see temperatures above 40C for three days in a row from Thursday to Saturday. This will shatter the city’s March record, and perhaps even surpass the April record in the process.

Denver in Colorado is forecast to surpass 30C on Saturday, almost 20C above the average temperatures for this time of year. This heatwave is anticipated to persist into next week and propagate eastwards, bringing much of the US under exceptionally warm weather by the middle of next week.