New Delhi, June 24 -- Millions of people across France woke up drenched in sweat on Tuesday after another night of scorching heat, with most of the population exposed to extreme and exceptional temperatures.

Temperatures will remain exceptionally high around the clock as the national weather service, Meteo France, placed 54 departments under a red heat wave alert.

In a country without widespread air-conditioning, schools, trains and sporting events remain impacted, while some 20 drowning deaths have been reported since the weekend.

Human-caused climate change is tied to increasing extreme weather, and U.N. climate agency projections say the next five years should shatter more heat records.

"Sunshine continues to dominate across France...