Meteorologists say "excess rainfall" has been recorded across the country. (File)
With no major heat waves recorded in the core zones so far and "excess rainfall" across the country, this summer is turning out to be unusual, say meteorologists.
Summer sets in March in the core heat wave zones of the north, central and east India, and intensifies in April and May until the first week of June, when the monsoon winds arrive. Apart from the northern and eastern plains, central India's Vidarbha-Marathwada region, Gujarat, and parts of southern India in Andhra Pradesh and Telangana are known as core heat wave zones, where temperatures rise above 45 degrees Celsius.
In western Rajasthan, the maximum temperature even crosses the half-century mark.
The India Meteorological Department (IMD) predicted above normal temperatures in core heat wave zones this summer. However, the temperature has not peaked to that level yet.
Instead, India received 25 per cent excess rainfall between March 1 and May 11, according to the weather department.
OP Sreejith, a senior scientist with the Long Range Forecast unit of IMD in Pune, said March recorded 47 per cent more rainfall than normal and April saw 8 per cent more.
"This is not a usual phenomenon," said IMD Director-General Mrutunjay Mohapatra.
Mahesh Palawat, the vice president of private forecaster Skymet Weather, said there are usually two instances of heat waves in April.
The IMD declares a heat wave when temperatures rise 5-6 degrees Celsius above normal. If it is above 7 degrees Celsius than normal, the IMD declares a severe heat wave.
Sathi Devi, head of the National Weather Forecasting Centre of the IMD, said there was one heat wave in Gujarat in April but it was not widespread.
This month, temperature in parts of Rajasthan rose above 40 but a western disturbance brought rains and pulled the mercury down again.
The official attributed the lower temperatures in the northern plains to the frequent western disturbances that brought rain and thunderstorms.
A western disturbance is a cyclonic storm originating in the Mediterranean and traversing across the central Asia. When it comes in contact with the Himalayas, it brings rain to the plains and hills. This is a crucial phenomenon in the winters.
The National Weather Forecasting Centre official said parts of east and south India have also been witnessing thunderstorm activities which have kept the temperatures below the normal.
May has seen two western disturbances. Another one is expected later this week.
"But the temperature could rise after May 16," Skymet's Mahesh Palawat said.