27 * ambient temp without wind I have sustained some damage. But in the earth I think your fine under your deck to a bit lower than that.
buy a cheap thermometer with a outdoor probe deal (
https://www.google.com/search?hl=en...rAhUJrp4KHXQDAK0Qlr4CegQIBBAG&biw=441&bih=739
So you can know what temp it is with the plant .
I set an alarm for 2 or 3 am to check