Delhi continued to reel under oppressive and warm weather on Wednesdayas the national Capital recorded a maximum temperature of 40.9 degrees Celsius at Safdarjung observatory while humidity levels oscillated between 51 per cent and 70 per cent.

The India Meteorological Department (IMD) predicts arrival of monsoon in Delhi by Thursday or Friday.

According to the IMD, the heat index (HI) is what the temperature "feels like" to the human body when relative humidity is combined with the air temperature.

HI is calculated for shady areas. Whereas, wet-bulb temperature is the lowest possible temperature that can be reached through evaporation of water in any given air condition. It takes into account temperature, humidity, wind speed, sun angle, and cloud cover, etc. And is considered the best metric to calculate and monitor heat stress on the human body.

A wet-bulb temperature of 35 degrees is considered the maximum limit of humidity that humans can handle. Beyond this, the body can no longer effectively cool itself through perspiration.

The IMD has issued an orange alert, warning of moderate rainfall in the city on June 30. The maximum temperature will come down to 33-34 degrees Celsius by July 1.

Senior IMD scientist R K Jenamani said there is a prediction of good rainfall in the city on June 30 and the arrival of the monsoon can be declared on Thursday or Friday.

According to IMD data, the monsoon covered Delhi 29 times in June and 33 times in July in the last 62 years. The IMD had in 2020 revised the date of monsoon arrival in Delhi from June 29 to June 27.

Since June 1, when the monsoon season starts, Delhi has received just 24.5 mm of rainfall against the normal of 66.7 mm. All of it came between June 16 and June 20.

The sizzling heat also pushed the peak power demand to 7695 MW on Wednesday, the highest in this month.

As per realtime data of State Load Dispatch Centre (SLDC), city’s peak power demand clocked 7695 MW at 3.10 PM on Wednesday while on Tuesday it was 7601 MW. The previous high in Delhi was 7409 MW recorded on July 2, 2019.