First Forty Degree For Delhi Today, Heat Wave Likely Till Mid-Week

Capital city, Delhi, is likely to get hotter this week, commencing today itself.  The base observatory, Safdarjung has so far recorded the highest day temperature of 39°C on 03rd April. The observatory recorded a maximum temperature of 38.2°C yesterday, a rise of about 2.5°C from the previous day. Mercury is likely to rise further today and is expected to remain in the low 40s for the next three days. Since the average pentad temperature around this time is about 35°C, it may amount to heat wave conditions, the first of this season, for the city.

Heat wave conditions for the plains are considered when the surface temperature reaches or exceeds 40°C. Essentially, this has a rider that the departure from the normal is 4.5°C or more. The heat wave is also considered when the day temperature touches 45°C or more. A severe heat wave is declared when the departure from the normal is 6.5°C or more. 

The national capital has a track record of registering maximum temperatures of 40°C or more in the month of April. In the last 20 years, the base observatory reached this mark every year except in April 20212, when the highest got arrested at 38.7°C on 04th April. Unusually, the highest temperature in that year was recorded in the first week of the month, defying the trend of scaling the extreme temperature in the last week of the month.

Though the national capital recorded temperatures in excess of 40°C in April 2024 and 2023, there was no heat wave registered as such. The reason being, the heat wave sweeps when the day temperature crosses 40°C and the departure from normal is 4.5°C or more. The pentad normal for the month keeps increasing and reaches 37°-38°C in the last week of the month. Therefore, the temperature has to reach 42°-43°C during those days to qualify for heat wave conditions. In 2022, the month of April had 9 heat wave days. The day maximum had exceeded 40°C on record 17 days in that month. The highest maximum also breached the 43°C mark on the last two days of the month.

There is a western disturbance reaching the mountains of North India tomorrow and staying put for the next 4 days. The system will impact the weather activity in the plains for nearly three days, between 09th and 11th April. However, the wind pattern will be influenced straight away. Delhi will witness a rise in day temperature, and it is likely to cross 40°C today. A similar trend is expected for tomorrow and the day after, when the temperature will stay in the low 40s. Heat wave conditions are likely between 07th and 09th April. The temperature will drop thereafter, and there is an outside chance of very light rain over the city and suburbs between the 9th and 11th of April. The temperature is likely to rise once again after the passage of the weather system.