Highest temperature ever recorded
On Monday afternoon, the temperature in Kumagaya City, Saitama Prefecture, north of Tokyo, was recorded at 41.1 degrees Celsius. It is the highest-ever in Japan.
Elsewhere, the temperature rose to 40.8 in Tokyo's Ome City, 40.7 in Tajimi City, Gifu Prefecture, and 40.3 in Kofu City, Yamanashi Prefecture.
It is the first time the temperature at a point in Tokyo hit the 40-degree mark since recordkeeping began.
Two high pressure systems
The country has recently been covered by two layers of high pressure systems. The Tibetan High is currently above the Pacific High, leading to clear skies and strong sunshine.
A Meteorological Agency official told reporters on Monday that the heat wave was likely to linger until early August due to the two systems. He said daytime highs may continue to be above 35 degrees in some areas.
"Dry Foehn"
Another factor is northwesterly winds. Warm air flowing down from mountains north of Kanto pushed up temperatures. This condition is known as a "Dry Foehn."
The winds also prevented cooler breezes from the sea reaching inland areas.
Too hot to enjoy the summer
Many outdoor events have been cancelled due to the temperatures. An elementary school in Tokyo suspended swimming lessons over the summer break.
The water temperature in the pool was 33 degrees. It's the first time the school has cancelled use of the pool because the water was too hot. The principal said it was a shame the children wouldn't be able to enjoy summer, but that safety comes first.
The weather is also putting the brakes on one of Japan's top summer events. Organizers say it is too hot to hold Kyoto's annual Gion festival.
The parade was scheduled for July 24th and would have featured about 1,000 people dressed in traditional kimono. It is the first time the parade has been canceled because of heat since it began in 1966.
As dangerous as a natural disaster
More than 22,000 people across the country were rushed to hospitals with symptoms of heatstroke last week. 65 of them died.
The Fire and Disaster Management Agency says both figures are the highest since recordkeeping began 10 years ago. Nearly half of those with symptoms were 65 or older.
Agency officials are urging people to use air conditioners and drink water, even when they are not thirsty.
Masaji Ono of the National Institute for Environmental Studies warns that another group of people is particularly at risk as temperature remains above 30 degrees. He says with the heat and humidity, Japan is a dangerous country for tourists to visit.