Due to the warm and humid air, the temperature will rise nationwide on the 10th, and it is expected that the maximum temperature will exceed 20 degrees in various places and will be as warm as early May. On the other hand, due to the effects of low pressure systems and fronts, the atmosphere is becoming very unstable, especially in eastern Japan.
Source
Maximum temperature exceeds 20 degrees in various places, atmospheric instability mainly in eastern Japan Beware of lightning strikes | NHK
