Weather officials are warning of high temperatures and humidity across Japan on Sunday, following the hot weather recorded in many parts of the country the previous day.
The Meteorological Agency says sunny weather raised temperatures on Saturday to mid-summer levels, mainly in areas along the Sea of Japan. Niigata Prefecture's Nagaoka City registered the highest temperature of 35.4 degrees Celsius.
High temperatures usually marked in the first half of July were seen also in some major cities. Osaka had 30.6 degrees, Fukuoka recorded 30.2 degrees, Nagoya saw 30 degrees and in central Tokyo it was 29.9 degrees.
The Tokyo Fire Department says that by 9 p.m. on Saturday 18 people in the capital were taken to hospital due to apparent heatstroke.
Weather officials are forecasting temperatures of about 30 degrees across the country again on Sunday, and are warning that humidity levels will also rise.
They are calling on people to take measures to prevent heatstroke by using air conditioners when necessary, stay hydrated, avoid continuous work or heavy exercise outdoors, and to take breaks as needed.
Officials also say extremely unstable atmospheric conditions may occur in wide areas from western to northern Japan on Sunday. They are advising people to be on alert for lightning strikes, wind gusts, including tornadoes, as well as heavy rain and hail.