For qualifying Friday night temperatures around 25-30 degrees C with no rain and almost clear skies.
On Saturday for the start of the race, heavy rain showers are expected with 28-30 degrees C air temperatures. Hours into the race a bigger low-pressure system is moving across the region with more continuous but lighter rain. During Saturday evening the night, the rain will subside and turn into light rain showers with clear skies in between. Temperatures expected to stabilize around 26 degrees, but climbing through the night as the rain disappears and could reach as high as 34 C.
Sunday morning the rain showers should completely disappear and temperatures should climb to about 29-30 degrees C.
Keep in mind the 9-hour time difference between Matsusaka Circuit and CEST. The highest temperatures are expected around midnight CEST.