Why roofs leak during snow but not rain ?

  When homeowners in South Jersey notice a roof leak, it often happens during the winter— not during heavy rain, but when snow is sitting on the roof . This can feel confusing, but the cause is usually very specific and preventable. Let’s break down exactly why this happens. 🧊 The Real Problem: Ice Dams The most common reason roofs leak during snow is something called an  ice dam . 🔍 What is an ice dam? An ice dam forms when: Snow builds up on your roof Heat from your attic melts the snow Melted water flows down toward the edges The colder edges refreeze Ice builds up and traps water behind it That trapped water has nowhere to go—so it starts  pushing back under your shingles . 💧 Why It Leaks During Snow (But Not Rain) 🌧️ During Rain: Water flows quickly off the roof Shingles are designed to shed water downward No blockage = no problem ❄️ During Snow: Snow melts slowly Ice blocks proper drainage Water sits on the roof longer Water gets forced  under shingles, fla...