New Delhi: The mercury surged to 49 degrees Celsius in Rajasthan's Phalodi -- the highest temperature recorded in the country this year -- as a sweltering heat wave stewed northwest India and some parts of the central region on Friday.

Official data showed that at least 23 places in Punjab, Haryana, Rajasthan, Uttar Pradesh, Gujarat, and Madhya Pradesh recorded maximum temperatures of 45 degrees Celsius or above on Friday.

The extreme heat will continue in parts of Delhi, Rajasthan, Punjab, Haryana, Chandigarh, west Uttar Pradesh and west Madhya Pradesh until May 28.

This means thousands of voters may face scorching temperatures when they step out to exercise their franchise in the sixth phase of the Lok Sabha elections on Saturday.

Around 11.43 crore people are eligible to vote in the sixth phase during which polling will be held in 58 seats spread across eight states and Union territories.

In Rajasthan, Phalodi logged a maximum temperature of 49 degrees Celsius on Friday, the highest recorded so far this year.

Jaisalmer and Barmer in the desert state sizzled at 48.3 degrees and 48.2 degrees. Akola and Jalgaon in Maharashtra reached 45.8 degrees and 45.4 degrees. Madhya Pradesh's Ratlam and Rajgarh recorded a high of 46.2 degrees and 46.3 degrees.

Maximum temperatures settled at 45.4 degrees in Haryana's Sirsa, 44.8 degrees in Punjab's Bathinda, and 45.5 degrees in Gujarat's Ahmedabad and Gandhinagar.

The Met office issued a 'red' warning for Rajasthan, Punjab, Haryana, Chandigarh, Delhi, west Uttar Pradesh and Gujarat, emphasising a "very high likelihood" of heat illness and heatstroke in all ages.

It said warm night conditions could further exacerbate heat-related stress in Uttar Pradesh, Punjab, Haryana, Delhi, and Rajasthan over the next four days.

High night temperatures are considered dangerous because the body doesn't get a chance to cool down. Increasing nighttime heat is more common in cities because of the urban heat island effect, in which metro areas are significantly hotter than their surroundings.

The punishing heat is straining power grids and drying up water bodies, triggering drought-like conditions in parts of the country.

According to the Central Water Commission, water storage in 150 major reservoirs in India plunged to their lowest level in five years last week, exacerbating water shortages in many states and significantly affecting hydropower generation.

Water levels in the Delhi stretch of the Yamuna River have dropped amid the sweltering heat, affecting water supply.

The city also saw power demand reaching a record 8,000 megawatts on Wednesday, with air conditioners, coolers, and refrigerators in homes and offices running at full throttle.

Severe and frequent heat waves are further burdening low-income households in the country, which often have poor access to water and cooling, and testing the endurance of outdoor workers toiling in the searing sun, forcing them to take frequent breaks.

Anna Walnycki of the London-based International Institute for Environment and Development said: "Low-income households have limited capacity to adapt to extreme heat because of poor access to water and electricity. In addition, the design and construction of informal houses often mean there is poor ventilation and little shelter from extreme heat." Experts say outdoor workers, the elderly, and children are at higher risk of heat exhaustion and heatstroke. According to the World Health Organization, more than 1,66,000 people died as a result of heat waves between 1998 and 2017.

India reported 3,812 deaths due to heat waves between 2015 and 2022, with Andhra Pradesh alone logging 2,419 fatalities, the government told Parliament in July last year.

People are less productive during hot weather, and children struggle to learn.

Shyamal Santra of the NGO Transform Rural India said studies show that students perform worse in tests when they experience a 'hot school year' compared to a 'cool school year'.

"With 15 per cent of government schools in India not having a functional electricity connection and many being single-classroom schools, heat waves disproportionately affect rural educational outcomes," he said.

In the absence of adequate cold-chain infrastructure, extreme heat can cause major damage to fresh produce.

Studies show India faces food losses worth USD 13 billion a year, with only four per cent of fresh produce covered by cold chain facilities.

According to a World Bank report, India could account for 34 million of the projected 80 million global job losses from heat stress-associated productivity decline by 2030.

With 75 per cent of workers in India experiencing heat-related stress, lost labour from rising heat and humidity could result in a loss of up to 4.5 per cent of India's Gross Domestic Product (GDP) (equivalent to approximately USD 150-250 billion) by the end of this decade, according to a report by the McKinsey Global Institute. 

Heat Wave in Dharamshala 

Following heat wave conditions, all government and private schools will remain closed on May 25 in Indora, Fatehpur, Jawali, and Nurpur subdivisions of Kangra district, officials said on Friday.

The intense heat wave conditions, which pose a risk to public health, are forecasted to continue for the coming days, the MeT office in Shimla had informed earlier, the officials said.

Deputy Commissioner, Kangra Hemraj Bairwa ordered the closure of all government and private schools on Saturday in the sub-divisions of Indora, Fatehpur, Jawali, and Nurpur in district Kangra.

On Friday, Una was the hottest during the day recording a maximum temperature of 40.6 degrees Celsius while Kangra recorded a high of 35.2 degrees Celsius, as per the MeT Office.

The MeT also issued a yellow warning of heat wave at isolated places in low hills till May 28.

The Deputy Commissioner of Una, Jatin Lalit had earlier ordered the closure of all government and private pre-primary and primary schools in the district on Friday and Saturday and said that in the schools where examinations are scheduled, the exams would be held from 7 am to 11 am.

Instructions were also given to provide all facilities like drinking water, fans, coolers or air conditioning in the examination halls of schools.