[kdog26372]

I did a little digging into these intake box snow valves...from what I gathered they are there to keep light dry snow from getting/sticking on the intake filter, freezing and then eventually melting into water and degrading the filter over the long term. When you plug this valve and drive in a blizzard or very snowy day (hence the extreme weather conditions part) you may end up getting snow on the filter and thus degrading some performance.

This is my understanding, but easy solution would be to examine filter if you just drove in a snow storm and if it's covered in snow, shake it off. I live in Chicago and will maybe drive in 2-3 snow storms in a season and will be using this procedure once I get my intake.