Photo/Illutration Water is sprinkled over a road with snow-melt piping as an anti-heat measure in Sanjo, Niigata Prefecture, on Sept. 3. (Natsuki Midorikawa)

The city of Sanjo, Niigata Prefecture, broke national temperature records when the mercury hit 40 degrees at 12:58 p.m. on Sept. 3, according to the Japan Meteorological Agency.

The agency said it is the first time temperatures of 40 degrees or more have been recorded in Japan in the month of September.

Weather experts pointed to three likely culprits that conspired to break the record.

First, it was already warm with clear weather and high atmospheric pressure. Second, southerly winds intensified due to Typhoon No. 9. And, finally, a type of dry, warm wind that crossed over the mountains--known as a foehn wind--blanketed the area.