Even the inside cupboard had the dang weevils in a hermetically sealed glass vessel.
Maybe it’s too cold for weevils here.
If bugs showed up inside your sealed glass jar it most likely means the eggs were already in the flour. Changing brands might be the first test. Freezing a couple days before storing might avoid the problem. In humid country keeping the flour in a tight contained with a small amount of heat, like a small light bulb, might keep the bugs away.
In my own dry country I just keep the stuff in it’s factory sack and bugs never show up even after years on the shelf. If I ever saw a bug I’d just burn the stuff and start over.