Windblown major rain and/or snow can force drinking water up and underneath even appropriately mounted shingles. Even worse are ice dams (frozen h2o/snow that builds up on roof edges), which often can wreak havoc by allowing drinking water to seep up below decrease shingles after which drip into your home. https://roofing04169.educationalimpactblog.com/41549452/roofing-secrets