Weather Bee: March shows two sides as heat gives way to pleasant weather

Pleasant weather cools India after early March heat; temperatures drop sharply, preventing one of the warmest months on record, IMD data shows.

Pleasant weather across much of India over the past week marks a sharp turnaround from the unusually warm first half of March, preventing the month from becoming one of the hottest on record, HT’s analysis of India Meteorological Department’s (IMD) gridded data shows. Here is how.

Sharp mid-March cooling reverses early heatwave trend across India, keeping overall temperatures near normal, IMD data shows. (Sanjeev Verma/ Hindustan Times)

Overall, this is only the 28th warmest March so far in terms of maximum temperature...

According to IMD’s gridded data, India’s average maximum temperature in the first 22 days of March is 31.35°C. This is only the 28th highest for this period since 1951, the first year for which IMD has published gridded data. It is also close to the normal of 30.89°C, which IMD considers the average for the 1981–2010 period.

To be sure, the month remains quite warm in terms of minimum temperatures. The average minimum temperature ranks as the seventh highest and is 1.10°C above normal.

…but was the sixth warmest by maximum temperature in the first two weeks

While March, on average, appears relatively normal in terms of maximum temperatures—the key metric as summer approaches—this was not the case at the start of the month. For example, the 40°C threshold was breached in the gridded data by March 6, or day 65 of the year, marking the third earliest such breach since 1951.

The average maximum temperature in the first 14 days of the month was 32.33°C, the sixth highest for this period, and 2.08°C above normal.

gfx (HT)

The overall average has been brought down by a sharp turnaround after March 14

The country’s average maximum temperature was above normal on all of the first 14 days of March, with a peak positive deviation of 3.03°C on March 5. Conditions changed dramatically from the middle of the month. The deviation shifted from 0.99°C above normal on March 14 to 0.71°C below normal on March 15.

Maximum temperatures have remained below normal on all subsequent days, with a peak negative deviation of 4.28°C on March 20. Such sharp downward deviations have brought down the month’s overall average.

gfx (HT)

The turnaround has occurred across almost the entire country.

This can be seen in the accompanying maps. Only around 7% of the country’s area was cooler than normal in the first 14 days of March. In the subsequent eight days, 89% of the country was cooler than normal, while only 11% was warmer than normal.

To be sure, both the upward and downward deviations have been less pronounced in peninsular and central India. This could be because the lack of western disturbances—storms originating in the Mediterranean region that bring rain to northern India at this time of year—led to the extraordinary warmth in the first half of the month. It is due to rain and cloud cover brought repeatedly by these systems that maximum temperatures have cooled thereafter. These systems do not usually have a big impact in central India and rarely affect peninsular India.

Map 1 (HT)

Map 2 (HT )