As few guys wrote here it’s the best way:
npm i -D @types/webpack-env
For me it works as expected, resolving issue with not recognized hot property.
In my project I’m using those versions:
"@types/node": "^8.0.19",
"@types/webpack-env": "^1.13.0"
I don’t know if question is still up to date but for my problem installing types for webpack help me.