Light rain and strong winds over the past two days in Delhi sent temperatures back to what they were a month ago. The maximum temperature on Wednesday was 29.5 degrees Celsius, seven degrees below normal. The minimum was 19 degrees Celsius, three degrees below normal.
The maximum on Monday was 40 degrees Celsius. Behind the sudden drop in temperature is a "very active" Western Disturbance over North India, whose effect is being felt in Himachal Pradesh, Haryana, Punjab, Rajasthan, Madhya Pradesh and eastern Uttar Pradesh.
The India Meteorological Department Wednesday issued a warning, asking authorities to remain alert and expect strong winds in parts of Uttar Pradesh, Punjab, Uttarakhand and Bihar.
On Wednesday, deaths in weather-related incidents were reported from Madhya Pradesh, Gujarat and Rajasthan.
In Delhi, however, the effect has been limited to lowering in temperature and strong winds.
"This type of weather is common in Delhi during the months of April, May and June. The significant drop in temperature is primarily because the Western Disturbance is very active. In Delhi, its effect will start to dissipate by Thursday. In Northeast and Central India, the effects are expected to last a day more," said a senior IMD official.
A Western Disturbance is a low-pressure wind system that originates in the Mediterranean region.
It travels over long distances, crossing Iran, Afghanistan, Pakistan and reaches India laden with moisture.
According to past data, April sees at least one squall and three thunderstorms. Last year, April saw three days with rain, five thunderstorms, two dust storms and one squall. In 2017, there were seven thunderstorms and three squalls.
The average maximum temperature between April 16 and 20 is 37 degrees Celsius.
According to IMD officials, temperatures are set to increase Thursday onwards. "Delhi will see a partly cloudy sky, with possibility of light rain Thursday. The maximum temperature is expected to be 33 degrees Celsius, while the minimum is expected to be 18 degrees Celsius," the official said.
By the middle of next week, the forecast says, the maximum temperature is expected to touch 40 degrees Celsius again.