US rainfall intensity by region (in/hr)
Typical published planning values — NOT a certified design. Actual gutter sizing depends on local rainfall intensity, roof geometry, valleys and debris; follow local code and the manufacturer’s data, and consult a pro for complex roofs. Structural roof-load, ice-dam / heat-cable and foundation/yard drainage are set by code and a professional — not engineered here.
Gutter sizing scales inversely with rainfall intensity: the harder it can pour where you live, the less roof a given gutter drains. The bands below are labeled planning typicals for the US 5-minute / 100-year design storm by region — confirm your local rainfall intensity. Use them with the gutter size calculator and the gutter-size drainage-area matrix.
| Region | Rainfall intensity (in/hr) | Note |
|---|---|---|
| Pacific NW / low | 2–4 in/hr | Steady but low-intensity rain |
| Northern / moderate | 4–6 in/hr | Moderate design-storm intensity |
| Midwest / Northeast | 5–7 in/hr | Heavier convective storms |
| Southeast / Gulf / high | 7–9 in/hr | Intense tropical downpours |
Labeled US 5-minute / 100-year planning bands — confirm your local rainfall intensity with NOAA Atlas 14 or local code. Higher intensity means a given gutter drains less roof.