As several parts of the country experience heatwaves, and with summer temperatures steadily on the rise, India is set to get its own heat index.
Starting this month, the India Meteorological Department (IMD) for the first time will introduce a heat index for the country. The index will be available on the IMD website, and will be updated every three hours across all weather stations.
A heat index – a measure of how hot it really feels – is calculated based on actual temperatures and relative humidity levels.
“Many times, when the temperatures are low but humidity is high, we feel hotter than what the temperature projects. And we don’t feel as hot when the temperatures are high and humidity levels are low,” said BP Yadav, director general, meteorology, IMD, Delhi. “The index will give citizens accurate and updated information on the heat conditions specific to their areas.”
In addition to introducing terminologies, the index will also comprise a warning colour code accompanied by information on health hazards if the temperatures and humidity levels cross a particular threshold.
For instance, a heat index between 40 and 54 with humidity levels less than 70% and more than 70% is termed is ‘uncomfortable’ and ‘uncomfortable sultry’. With yellow and orange as warning colour codes respectively, the health hazards read “heat cramps and heat exhaustion likely”. Similarly, a green colour code with a heat index less than 40 is ‘comfortable’ with no health hazards, while a heat index of more than 54 means ‘highly uncomfortable hot’ (orange) and ‘highly uncomfortable sultry’ (red) indicating a likelihood of heat stroke or sun stroke.
With 2015 as the warmest year since 1850, and this year showing similar trends, KS Hosalikar, deputy director general, western region, IMD, said, “The heat index is in the backdrop of indications that temperatures are rising affecting health, agriculture and also industries. Understanding the severity of the summer, we developed this index that will help a cross section of the population such as public, agriculturists and even sportspersons.”
Calling it experimental, Yadav said the heat index will be improvised for the next summer after consultations with various stakeholders.
An 2014 analysis by the Pune-based India Meteorological Department (IMD) revealed that heat waves and severe heat waves over India have increased over the last 50 years. More than half the number of weather stations – 57 of 103 – were hit by heat waves from March to July on an average of 550 days between 1961 to 2010. Severe heat wave was observed for an average of 60 days with18 of the 103 stations most affected over five decades.