Delhi recorded an unprecedented maximum temperature at 48 degree Celsius today. (FILE PHOTO)

Mercury touched 48 degrees Celsius in Delhi's Palam area today - creating a record high for the national capital in June -- as north India struggles under an unrelenting heat wave. The temperature, however, was lower at Safdarjung, roughly 14 km away. The temperature recorded there was 45.6 degrees Celsius.

"It was 48 degrees at Palam today, an all-time high. The earlier high was 47.8 degrees Celsius recorded on June 9, 2014," Mahesh Palawat of Skymet told NDTV.

The all-time record for Delhi is that of 48.4 degrees Celsius, recorded on May 26, 1998. In May 2016, Phalodi in Rajasthan recorded India's highest-ever temperature of 51 Celsius (123.8 Fahrenheit).

Some relief is expected only after tomorrow night -- the Indian Meteorological Office has predicted thunderstorm with "gusty winds".

IMD scientist Devendra Pradhan told NDTV, "We issued a red alert this morning for Delhi. People can expect some decline in temperature only from June 12."

Heat wave is declared when temperature remains at 45 degrees and above for two days running. It gets the "severe" tag when mercury touches 47.

Temperature of 48 and above has been mostly recorded in Rajasthan this summer -- Churu has been the hottest place for days.

Exactly a week ago, 11 of the 15 hottest places in the world were in India, the rest were in neighbouring Pakistan, weather monitoring website El Dorado reported.

The pattern of frequent heat waves in the country is part of the climate change that is making itself felt across the globe.

Last year was the sixth-warmest since 1901, when preserving weather records started in the country. Since 2004, the country has experienced 11 of the 15 warmest years.