A blistering heat wave has swept India, with record-breaking temperatures in the northwest part of the country.
Rochester has never seen temperatures even close to the 120 degrees Fahrenheit recorded in parts of Delhi on May 30. A 40-year-old factory worker became India’s first heat-related death of the year, according to The Indian Express newspaper.
What causes such extreme heat? And what does it feel like to be in such sweltering, humid temperatures?
What is a heat wave?
There are specific criteria that must be met for a heat wave to be declared in India, which typically sees its hottest days between March and June. The temperature must exceed 104 degrees in the plains or 86 degrees in hilly regions to be considered, according to the World Health Organization.
From there, the remaining criteria are either a departure from normal of 8 to 11.5 degrees, or a maximum temperature exceeding 113 degrees. When the criteria are met at two monitoring stations across a two-day span, a heat wave is declared on the second day.
The conditions to create a heat wave typically involve a high pressure system, or anticyclone, which extends through the lower atmosphere, said Scott Rochette, professor of meteorology and chair of the earth sciences department at SUNY Brockport.
“It’s a stagnant system that doesn’t move very quickly, which is why the conditions remain so hot for so long,” Rochette said.
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Rochester heat waves
While Rochester has seen plenty of near-record temperatures this year, it is insulated from more extreme heat by its location and infusions of cooler air from the north.
“We still get heat waves here — there’ll undoubtedly be one or two or even three this summer — but they don’t last for long,” Rochette said.
The National Weather Service does not have a strict definition for heat waves, due to variability in climate across the country. The Buffalo office generally defines a heat wave locally as three or more consecutive days with a heat index of 95 degrees.
Heat index factors in the relationship between air temperature and relative humidity to illustrate how the temperature feels to the human body. A heat index of 95 degrees, for instance, can be reached in different combinations such as 86 degrees with 70% humidity or 90 degrees at 50% humidity.
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Heat-related health impacts
What does 120 degrees feel like?
It’s a question Rochesterians might struggle to comprehend, with the city’s highest recorded temperature, 102 degrees, coming on consecutive days in July 1936.
Rochette compared the conditions to the feeling of walking into a sauna from room temperature conditions. It’s a shock to the system, which can make conditions unsafe, especially for those with sensitivity to heat.
The health impacts of heat include cramps, exhaustion, heatstroke and hyperthermia, according to WHO. It can worsen chronic conditions, like cardiovascular or respiratory diseases, and alter human behavior and air quality.
“The record heat we are seeing in India right now is dangerous, especially for the young, the old, and those with compromised immune systems,” said Joel Myers, AccuWeather founder and executive chairman.
Extreme temperatures and climate
A heat wave in lower elevations of the western United States, including the potential for “excessive, dangerous heat” in California’s Central Valley, is expected as soon as June 5, according to the Weather Service’s Climate Prediction Center. The excessive heat risk includes the potential for record overnight lows and daytime highs, with the latter reaching at least 100 to 105 degrees.
The extreme heat in India is expected to persist into the weekend, though should be less extreme than the peak around 120 degrees, said Jason Nicholls, AccuWeather lead international forecaster, in a statement. Temperatures are expected to remain overnight, however, with lows in the mid 80s.
Where India is located affects the amount and severity of extreme heat in the region. Located at or below the latitude of places like Florida and Texas, there is more direct sunlight from a sun higher in the sky. Being closer to the equator, along with humidity from sources like the Indian Ocean, can generate hot and humid conditions, Rochette said.
Relief from the record-breaking heat usually comes when monsoon season arrives, but less heat can be offset by greater humidity.
Global temperatures could become significantly higher than current climate models predict, Myers said.
“While there is much work to be done in this area of research, what we do know is that the impacts of climate change and global warming will be highly local, and the warming will be unevenly distributed,” he said. “Some places on the planet like India will see an even higher increase in temperatures than the global average.”
— Steve Howe covers weather, climate and lake issues for the Democrat and Chronicle and is training for the Boilermaker. An RIT graduate, he returned to Rochester after working around the state and in Utah. Share with him at showe@gannett.com.
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