Parma, OH rainwater: 37,348 gallons off a roof
Parma, OH: gallons off the roof each year
37,348gallons a year
That is a 1,500 sq ft asphalt roof under Parma, OH's normal 47.0 inches of rain, about 795 gallons for every inch that falls.
In Parma, OH a single barrel does most of the work. Storms come often enough that a small tank refills before it runs dry, and a bigger one would mostly sit full.
Rainfall: NOAA 1991-2020 climate normals, the Parma 1.8 Se station (1.8 mi away). Parma, OH ranks 2nd wettest of the 176 cities covered in Ohio.
Month by month in Parma
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 3.17 | 2,520 | |
| Feb | 2.79 | 2,218 | |
| Mar | 3.44 | 2,734 | |
| Apr | 4.28 | 3,402 | 9 |
| May | 4.68 | 3,720 | |
| Jun | 3.78 | 3,004 | 71 |
| Jul | 5.38 | 4,276 | |
| Aug | 4.20 | 3,338 | 19 |
| Sep | 4.26 | 3,386 | 11 |
| Oct | 3.98 | 3,163 | 46 |
| Nov | 3.67 | 2,917 | |
| Dec | 3.36 | 2,671 |
Jul is the wettest month (5.38 in, 4,276 gal off the roof); Feb the driest (2.79 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
Which tank size is worth it in Parma
Best fit: one 55-gallon barrel, which delivers about 112 gallons to the garden in a normal year (71.9% of its need).
If you set one up, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Parma's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 112 | 35,736 |
| 110 gal | 112 | 35,736 |
| 165 gal | 112 | 35,736 |
| 275 gal | 112 | 35,736 |
| 550 gal | 112 | 35,736 |
| 1,000 gal | 112 | 35,736 |
| 1,500 gal | 112 | 35,736 |
| 2,500 gal | 112 | 35,736 |
| 5,000 gal | 112 | 35,736 |
Simulated storm by storm through a normal year using the station's count of days with 0.1 in or more of rain each month.
Is rainwater collection legal in Ohio?
Legal. Ohio regulates rainwater cisterns used as a drinking-water source as private water systems (OAC chapter 3701-28): local health department permit, continuous disinfection and filtration. No state rule restricting non-potable collection or storage size.
Checked against the current source on 2026-11-06. Source