Japan on Monday recorded its highest ever temperature of 41.1 degrees Celsius in Kumagaya in Saitama Prefecture, around 80 kilometres from the capital Tokyo. The pan-nation heatwave has led to at least 40 deaths, with 11 people dying from suspected heatstroke on Saturday alone, according to The Japan Times.

The Japan Meteorological Agency said that the previous highest temperature was 41 degrees Celsius in the western prefecture of Kochi in August 2013, The Independent reported. In Tokyo, the temperature reached a high of 40.8 degrees Celsius in Ome, said the weather agency. It has issued a warning for high temperatures in most parts of the country, above 35 degrees Celsius for most of Honshu, Shikoku, and Kyushu islands, said a CNN report. Hokkaido, located in the north, has been the only main island to have escaped the heat.

In a statement, the meteorological agency said that “the potential for heat illness is higher than usual”. It asked people to drink enough water, use air conditioning, and stay away from direct sunlight whenever possible. It advised them to avoid outdoor exercise and seek medical attention as soon as any heatstroke-related symptoms occur.

The Tokyo Fire Department said 3,091 requests were made for ambulances in the capital on Sunday, the most for a single day since the department started emergency medical operations in 1963, reported Kyodo News. Most of them were from people affected by the heatwave.

Joel N Myers, president and founder of Accuweather, which monitors and charts weather around the world, said that the toll could reach thousands before the heatwave ends. He warned that the health of elderly and patients suffering from asthma and heart issues could also decline. “Heat exhaustion and stroke, dehydration, migraines, loss of sleep and mood alteration can all occur due to dangerous heat,” he said.

The soaring temperatures have also impeded the continuing relief efforts that were launched after Japan witnessed its deadliest flooding in decades earlier this month. At least 222 people are confirmed to have died in the floods.

South Korea, Japan’s neighbour to its west, has also experienced high temperatures recently. Yonhap news agency said that the temperature in Gangneung, less than 170 km east of capital Seoul, recorded the highest-ever morning low of 31 degrees Celsius at 6.45 am, reported AP. The morning low in Seoul was 29 degrees Celsius.