May chill: Why did Delhi-NCR witness fog in the hottest month?

Delhi-NCR woke up bewildered on May 4 as a layer of fog engulfed the entire region. Visibility reduced to just about a few metres. Some senior citizens had to take out their winter clothes. Social media immediately became active. Some said that it was surreal. Others said that winter had taken a U-turn. But of course! Fog in an otherwise hot month of May was highly unusual.The Times of India’s Senior Editor Amit Bhattacharya says visibility at the IGI Airport was recorded at 800 metres, which is shallow fog. This is unusual in May. What was the reason for the early morning fog? It had heavily rained a day earlier, and the temperatures were low. A lot of moisture with low morning temperature is a perfect recipe for fog. There was fog from 6 am to 8 am at the IGI Airport. Minimum temperature on May 4 was the lowest in 41 years. Why?In the past 10 days, three Western Disturbances have hit the region back-to-back. Western Disturbance is a wave of stormy weather that comes eastwards from Central Asia and hits the mountains in north India. This leads to rain and a drop in temperature. Three consecutive Western Disturbances at this time of the year is unusual. What led to 15.8 degrees Celsius temperature in the morning - as was recorded at Safdarjung – was this spell of low temperatures in the last 10 days. The last time minimum temperature went below 16 degrees Celsius was on May 2, 1982 — 41 years ago. It is unusual but the result of a cumulative number of Western Disturbances hitting the region and bringing temperatures down over a period of time. Is this freak weather related to climate change?The frequency of extreme weather events will increase as the world warms up. The last instance when temperature fell below 16 degrees Celsius was in 1982. Before that it was in 1969. So, temperatures have fallen only thrice in the month of May in the past 123 years. This is what we call “once in a 40-year event”. We can expect this in normal circumstances in 40 years. But in a climate change scenario, this can happen more frequently. In climate change the frequency of extreme weather events will increase with time as the Earth warms up. This is what we are seeing in the recent years. Will the weather remain pleasant, or become hot in the next few days?In the first three days of May alone, over 30 mm of rainfall was recorded at Safdarjung. At other stations it was even more. Normal rainfall for the entire month of May is 30 mm. So, we have already crossed the normal for the entire month. Forecast says that rain activity will decrease. We may get light rain around the weekend. But weather models do not show much rainfall for the next 10 days. It means that temperatures will rise and we will get a feel of the May heat. Will the weather change have an impact on crops?I don’t think so. The winter crop has already been harvested and the summer crop is yet to be sown in most places. At some places, short duration crops are sown in between. But most of North India may not see much impact. In fact, rainfall in May is good for retaining soil moisture, which might help when sowing takes place in a few weeks. Audio Production: Sahil Gupta