Ideas to help potatoes through hot weather conditions?

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I live in Nagano in Japan. It is described as having a humid sub tropical climate bordering on humid continental. This is snowy and cold between mid December to early March in winter, cool spring with frost risk up till mid April, Rainy in June and mid July and roasting hot between mid July to late August/ Early September, Frost returns from November.

May should be the perfect weather for potato growing here in Nagano with normal temps overnight meant on average about 10-11 and daytime temps usually averaging around 22 C. Instead of this, the last three weeks has seen some extremely unstable weather conditions, which has been playing havoc with my amatuer gardening efforts and particularly growing potatoes. We had frost and snow about two weeks ago! Very unusual. This week the weather has swung to swealtering 29\31 C temperatures and a heatwave (usually this is the weather for July) Unfortunately, Nagano is hitting the hottest temperatures in the country, because its inland. fortunately this weather is set to cool down from tomorrow.

What I would like to know is, What are peoples experiences of growing potatoes in warmer weather?

I am growing TPS seedlings, planted out last week! and also have 21 Burlap sacks of seed potatoes. These are above ground and covered in rice husk mulch. A number of the regular potatoes (grown from seed clones) have developed flower buds, but seem to be waiting for temps to cool down so they can set to flower.

I have read a few articles saying that the ideal potato growing conditions based on outside temperature and soil temperatures are as follows

root growth occurs with soil temps of between 10-35 C (50-95 F)
but optimum soil temps are 15 - 20 C (59-68 F)

leaf growth is said to occur at outside temps of between 7- 30 C (45 -86 F)
but optimum growth is possible when temps are between 20-25 C ( 68-77F)

Also read that a study showed potato tubers stopped growing when temps went above 28.5 C.

So,
What are peoples experiences of growing potatoes in warmer weather?

What methods have folks used to help help their potatoes survive hotter temperatures above their optimum growing temperature ranges?