Scalding heat to sauna swelter, the city has seen two faces of summer in a matter of days.
If dry and hot winds like the loo that blows across the north Indian plains in summer played villain last week, the end of the record-breaking heatwave has brought back the familiar foe: high humidity.
Metro analyses the change and tells you how to survive the summer switch-hit.
How has the weather changed?
The Met office had declared a heatwave on April 22 after the day’s weather fulfilled the condition of the maximum temperature rising at least five degrees above normal to hit 40 degrees Celsius or higher.
The already dry weather got drier over the next two days as the mercury kept climbing, sucking moisture out of the air. Last Friday’s high of 41.2 degrees Celsius equalled the record for the highest temperature in April in a decade. Not only that, the heatwave continued till Saturday, another April record.
The change started on Sunday with incursion of moisture. The Celsius descended but humidity soared, making Calcuttans even more uncomfortable than they were when the dry winds were blowing.
For the record, rain still isn’t on the radar.
Why has the weather changed?
Meteorologists had blamed the extremely dry weather and the heatwave last week on the absence of weather systems that normally draw moisture from the Bay of Bengal in summer. The lack of clouds not only allowed the Celsius to rise, the city was also denied its share of thunderstorms. April usually brings at least three squalls to Calcutta. There has been none this year.
On Sunday, a high-pressure belt that was far off to the south over the Bay of Bengal moved closer to the coast while a low-pressure trough stretching across the state intensified. Together, they contributed to the increase in relative humidity. Alas, they haven’t been able to bring rain relief.
What difference has it made?
The temperature may have come down but discomfort has increased because humans are more sensitive to an increase in humidity than they are to a rise in temperature, if both are high.
Last week, Calcuttans were seen covering their faces to keep their skin from getting burnt and avoid inhaling the hot air. Covering the face now would be counter-productive because of excessive sweating.
“All through last week, I was being forced to wrap my dupatta around my face every time I went outdoors during the day. On Monday, I did the same thing out of habit but within a few minutes, my dupatta was dripping with sweat,” said Anita Singh, 32, a resident of Lake Town.
Aritra Munshi, who is preparing for the civil service exams, said he preferred the dry heat to the sweaty feeling. “When it was dry, it was less uncomfortable indoors. You felt the sting of the sun only while stepping out. I am now in my room and the fan is at full speed, but I am sweating.”
What precautions to take?
The human body maintains a temperature of 98.6 degrees Fahrenheit by thermoregulation, a system that helps it maintain an inner core temperature through sweating in hot weather and shivering in winter. Sweat evaporates easily when relative humidity is low, but when it is high, the air is more saturated with water and sweat lingers to cause discomfort.
But dry heat can be tricky. “Heatstroke is common in dry weather because people don’t realise how much they are sweating as the sweat evaporates easily and they don’t take supplementary fluids,” said Arindam Kar, head of critical care at Medica Superspecialty hospital.
In dry-heat weather, it is advisable to cover the face with a cloth and wear sunglasses as hot winds tends to scald the skin and can enter the body through the nostrils or ears to cause hyperthermia, a condition in which the body temperature shoots up abnormally.
But in humid conditions, the face shouldn’t be covered. “You can catch a cold if you have your face covered and sweat,” said critical care expert Subrata Maitra.
Nutritionist and t2 columnist Hena Nafis advises drinking a lot of fluids. “Back from a trip to Saudi Arabia on April 20, I was shocked to find my city hotter and drier than the desert kingdom. Now the dry loo is less but it’s still very hot, so my advice is to stay hydrated. Drink barley water, iced tea, bael, juices and lime water.”
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