Delhi experienced heatwave conditions for the third consecutive day on Thursday as the mercury shot up to 43.1 degrees Celsius, the India Meteorological Department said. This was the hottest July day in the national Capital since July 2, 2012, when the city had recorded a maximum temperature of 43.5 degrees Celsius, according to PTI.

For Friday, the weather department has issued a heatwave alert for Delhi, Haryana, Punjab, east and west Uttar Pradesh and Rajasthan. Thunderstorms with lightning is expected at isolated places in these regions.

India Meteorological Department Director Mrutunjay Mohapatra said the intensity and area coverage of the heatwave could decrease after Friday due to the south-westerly winds from the Arabian Sea. The humidity will, however, remain high.

Mohapatra added that there was no chance of monsoon rains in Delhi and the neighbouring areas till July 7.

He said the progress of monsoon has stalled since June 19 and the break is likely to continue till the second week of July, resulting in heatwave conditions in western and central India, reported The Indian Express.

“Till the time that the monsoon break happened, the monsoon had already covered most parts of the country, except parts of Rajasthan, Punjab, Haryana and Delhi,” the weather department chief said. “From July 7, there is likely to be some improvement, and then in the third and fourth week of July things will normalise.”

On Thursday, the Safdarjung Observatory in Delhi, which provides representative data for the city, recorded a maximum temperature of 43.1 degrees Celsius. Meanwhile, the monitoring station in Mungeshpur recorded up to 45.2 degrees Celsius, the highest in the city, and eight notches above normal.

For the plains, a heatwave is declared when the maximum temperature goes up to 40 degrees Celsius or more and is least at 4.5 degrees above normal. A severe heatwave is when the normal temperature is 6.5 degrees Celsius more than the normal.

The heatwave condition in the national Capital region has coupled with poor air quality. A bulletin released by the Central Pollution Control Board on Thursday evening pegged the Air Quality Index in Delhi at 266, which falls in the “poor” category. The air quality was “very poor” and “moderate” in Noida and Gurugram, respectively.

On Thursday morning, the live tracking system of System of Air Quality and Weather Forecasting And Research, or SAFAR, showed “poor” levels of PM10 particles across all observatories in the national Capital. The PM2.5 levels also varied between “moderate” and “poor” levels.

Particulate matter smaller than 2.5 microns (or about a ten-thousandth of an inch) is particularly dangerous to human health. Such particles are small enough to travel deep into the respiratory system, potentially impairing lung function.