One night last week HR professional and Matunga resident Purvi Ashar was sleeping under a thick blanket with the fan switched off. The very next night the blanket was back in the closet and fan whirring overhead. In Ashar’s office in suburban Malad, the heaters are off and the air conditioners are on. This is how Ashar, like the millions of other Mumbaikars, experienced the heat wave that started so suddenly last week.
Without warning or preamble, summer has arrived in Mumbai. This Tuesday was the hottest day in February in 46 years. The city got a summer slap with the maximum temperature reaching 39.1 degrees Celsius, just below the record high of 39.6 C measured in 1966. Old-timers remember that Mumbai hardly ever used to get this hot even in high summer. Because of this sudden change, people are trying to avoid venturing out during the day.
In midtown Santacruz on Tuesday, February 21, the gap between maximum and minimum temperatures was an immense 21.3 C. The minimum on that day was a pleasant 17.8 C. Such a temperature range in a single day is difficult for the human body to adjust to — and is rare in Mumbai, a city which otherwise witnesses little seasonal variety despite the rising average temperatures of recent years. The suddenness of this week’s change explains the rash of people calling in sick.
Pravin Shah, a doctor, says he has seen a 25-30 per cent increase in the number of patients at his clinic in suburban Kandivali. The majority of cases are of viral fever involving sore throats, cough and cold. “Such varied temperatures can trigger problems like asthma, conjunctivitis and even high fever,” he says.
The heat has been attributed to the dry easterly (from the east) winds that were prevailing over a cloud-free Maharashtra state. Under normal conditions in any coastal region, unlike in inland cities like Pune or Nagpur, temperature extremes are balanced by the juxtaposition of sea and land.
During the day, the land takes up the sun’s heat faster. The air above the land also heats and rises; this causes cooler air from over the sea to be sucked towards land, easing coastal temperatures. During the night, the sea retains heat longer, and air above the sea rises, drawing cooler air from inland towards the coast, thus again moderating coastal temperatures.
This engine of temperature regulation seems to have been temporarily interrupted in the Mumbai coastal region. This week the sea breeze did not blow, so the temperature has risen. Officials of the India Meteorological Department (IMD) have said, however, that the end of February often does show such variations.
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IMD director Bishwombhar Singh has said that easterly winds are causing the change. On Tuesday and Wednesday, the weather was hot and dry and humidity was as low as 14 per cent (100 per cent is during rainfall) until after 1.30 pm. After that the sea breeze brought moisture in and helped reduce the temperature.
Colaba, a green area of south Mumbai with the sea on both sides — unlike busy Santacruz — recorded a maximum temperature of 35.2 C (5 C above normal), and a minimum of 22.3 C, or a total variation of only 12.9 C.
“We measure the day’s temperature at about 1 pm and 7.30 pm with two centre points — Colaba and Santa Cruz. The sea levels are measured at about 75 km from the land,” says IMD’s Singh. “Summers witness an increase in range and speed of the western winds.”
As to weather-related human ill-health, one comparative case is those parts of Europe that are affected by the Föhn, a warm wind off the dry northern slopes of the Alps. The Föhn can raise the local temperature to as much as 30 C within a few hours. These winds are associated with illnesses ranging from migraines to psychosis.
“The sudden transition from winter to summer has impacted many people’s health with respiratory diseases, viral fever, running nose and migraines,” says Dr Ameet Thakkar, another GP with Genesis Specialty Centre in midtown Wadala. “Be careful with your diet,” he recommends, “and eat more leafy vegetables and drink lots of water.”
According to IMD forecasts, day temperatures are likely to stay at 32-35 C for at least the next week. The blankets can be packed away.