The Tokyo Fire Department says 107 people were taken to hospitals in the Japanese capital over the weekend due to possible heatstroke.
Central Tokyo saw the mercury top 30 degrees Celsius on Saturday and Sunday as an unseasonal heat wave hit the country.
Fire Department officials say the number of heatstroke patients treated in hospitals in Tokyo has reached 237 so far in May. The figure for the same period last year was 142.
Last Friday, 12 high school students at an athletic meet in Tokyo's Itabashi Ward were taken to hospitals because of possible heatstroke.
The officials are urging people to drink a lot of water, avoid sunlight, ventilate their rooms, and take other precautions against heatstroke.