Yahoo.com's whether for Japan seems strange
Yahoo's Whether Forcast screen is quite good! I'm enjoying it from Japan.
However, seems the tempareture values look strange. e.g. it's 2018/5/4's min tempareture Sapporo-Japan. According to Japan Whether Buerrow, it's 8 degrees Celsius.
Yahoo.com's whether says it's 1 degrees Celsius. Too big error isn't it?
World Meteorological Organization defines how to measure Temperature, and seems Yahoo.com's whether for Japan does not follow the definition. The whether source is what? And is't it possible to change the whether source to a better one?