It has been a historically chilly start to May in India, thanks to an unusually strong low-pressure system that moved in from the west, sweeping humid air from the Arabian Sea across the subcontinent. The resulting overcast skies reduced the heating effect from the sun, which combined with the brisk winds and abnormally high rainfall to lower temperatures significantly.
May is considered the final month of the Indian summer, before the monsoon season begins in June, and is the hottest time of the year for many parts of India. However, in the past week large parts of the country have been about 10C colder than normal, with many weather stations in northern India observing record minimum temperatures for the month.
The effect has been noticeable in Delhi, where temperatures failed to exceed 30C (86F) between Sunday and Tuesday, in comparison with the average daily high of 39.9C (103.8F). Residents on Thursday morning woke to shallow fog filling their streets, a phenomenon almost unheard of in the city. Temperatures were as low as 15.8C (60.4F), making Thursday the third-coldest May morning since modern records began in 1901.
Temperatures are expected to slowly return closer to normal over the next few days, but there are some concerns that this unusually cold and humid period could delay or weaken the onset of the monsoon.
Meanwhile, the eastern US has been experiencing some unusually cool and unsettled weather this week, thanks to a lingering area of low pressure that is slowly moving out into the Atlantic. However, a warm and humid airmass pushed north through Texas on Thursday morning, with the sudden contrast bringing ideal conditions for the development of thunderstorms.
“Strong to severe” thunderstorms affected eastern Colorado, northern Texas, and Oklahoma on Thursday, and are expected to move eastwards this weekend, bringing a risk of localised flooding, large hail and isolated tornadoes.
Also in the US, north-western areas experienced abnormally warm and dry weather this week, melting snow at high altitudes. As weather turns unsettled over the coming days, there is concern the increase in precipitation could cause flooding along rivers and streams already swollen with snowmelt, with several flood warnings in place.
