NEW DELHI — One of India’s longest and most intense heat waves in decades, with temperatures reaching 123 degrees, has claimed at least 36 lives since it began in May, and the government has warned that the suffering might continue as the arrival of monsoon rains has been delayed.

India’s heat waves have grown particularly intense in the past decade, as climate change has intensified around the world, killing thousands of people and affecting an increasing number of states. This year, the extreme temperatures have struck large parts of northern and central India, with Rajasthan, Madhya Pradesh, Uttar Pradesh and Maharashtra among the worst-hit states.

Anup Kumar Srivastava, an expert at India’s National Disaster Management Authority, said the number of Indian states hit by heat waves had grown to 19 in 2018 from nine in 2015, and was expected to reach 23 this year.

“This year, the number of heat wave days have also increased — and it’s not just day temperature, night temperatures have also been high,” he said.

Mr. Srivastava said that imminent storms would bring down temperatures in some areas, but that heat waves might pick up again until the monsoon rains arrive.

Twice in the past week, the temperature in the Churu area of Rajasthan, in northern India, reached 123 degrees Fahrenheit (about 51 Celsius). India’s Meteorological Department warns that heat that extreme brings a “very high likelihood of developing heat illness and heat stroke in all ages.” Several other parts of the state have recorded temperatures surpassing 118 degrees.

The medical authorities have canceled leaves for doctors at hospitals in Churu as the number of patients has shot up. In Madhya Pradesh, in central India, schools have remained closed.

Prolonged temperatures of at least 113 degrees are considered a heat wave, while prolonged temperatures of 117 degrees or higher are considered a severe heat wave.

In the capital, New Delhi, temperatures reached a record 118.4 degrees on June 10. Clouds on Tuesday promised rain, but largely failed to deliver. Dust storms the next day lowered temperatures to around 100.

Heat records around the world are more likely to be broken as average temperatures climb upward because of rising greenhouse gas emissions.

While there are variations year by year, the global trend line is clear: the five warmest years in recorded history have been the last five, and 18 of the 19 warmest years have occurred since 2001.

A recent analysis of climate trends in several of South Asia’s biggest cities found that if current warming trends continued, by the end of the century, heat and humidity levels would be so high that people directly exposed for six hours or more would not survive.

The latest victims of this year’s weekslong heat wave were four people, ranging in age from 69 to 80, who died in Uttar Pradesh on Tuesday during a journey on a train that lacked air-conditioning.