GreenDeck Climate Commons • rainwater planning

Turn weather into a clearer plan for your property.

Estimate one rain event, look up a local forecast, and compare storage goals before deciding what deserves a site-specific design.

01 · EVENTSee the rain on your roof.

Translate an inch—or a live forecast—into water volume.

02 · LOCATIONCheck the local context.

Use an opt-in public-data lookup for the next 24 hours.

03 · STORAGECompare a storage goal.

Understand the tradeoffs before choosing a cistern.

01 · rain event

How much water does this event send to your roof?

Start with the roof area that drains to the system—not necessarily the full roof.

02 · location-aware forecast

Bring the next rain event into the estimate.

Enter a U.S. street address to look up a public forecast. The planner will apply the estimated next-24-hour rainfall to the event calculator above.

Find a local forecast

Use a complete street address only if you are comfortable sharing it for this opt-in public-data request.

U.S. street address

Opt-in lookup: the entered location is sent to the U.S. Census Geocoder. Coordinates are then sent to the National Weather Service. This page does not save the location.

03 · cistern scenario

Choose what you want the cistern to do.

Rainfall averages estimate annual harvest; they do not by themselves determine a safe or useful cistern size. Pick a storage goal to see a transparent planning range.

Primary storage goal Hold this selected rain eventUse the rainfall amount in the event calculator. Bridge a dry-season use periodSet a daily outdoor-water target and number of days. Balance both goalsUse the larger of the event and dry-period targets.

Local annual rain normal (in / year)

Daily outdoor-water target (gal / day)

Dry-period target (days)

For a local baseline, enter the official rainfall normal for the nearest appropriate station or grid cell. NOAA’s 1991–2020 Climate Normals are a good U.S. starting point.

Useful planning starts by naming the uncertainty.

Each inch of rain on one square foot of roof produces about 0.623 gallons. That makes roof area and rain depth a solid first estimate.

But a cistern is not sized from an annual average alone. The real question is how much water arrives in each season, how much storage is already full, how quickly water is used, and where excess water can safely go.

Want a site-specific rainwater plan?

GreenDeck can help translate roof runoff into practical options for storage, planting, and safer drainage.

Plan a GreenDeck consultation

Planning estimate only. Confirm dimensions, local requirements, overflow routing, and final system design before construction.