A study by the National Environmental Engineering Research Institute (Neeri) in Nagpur has found a “very strong” correlation — up to 85% — between the increase in the average day temperature and the reduction in Covid-19 spread for select cities in the country and for states like Maharashtra and Karnatakaas a whole. Neeri, a constituent laboratory of the Council of Scientific and Industrial Research, based its research on a mathematical model. It sourced Covid-19 case data from the World Health Organisation and temperature data from India Meteorological Department. It studied the average real time temperature and relative humidity and their relationship with the rising Covid-19 cases in Maharashtra and Karnataka.