Cairo, GA rainwater: 40,487 gallons off a roof
Cairo, GA: gallons off the roof each year
40,487gallons a year
That is a 1,500 sq ft asphalt roof under Cairo, GA's normal 50.9 inches of rain, about 795 gallons for every inch that falls.
In Cairo, GA 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 Cairo 1sw station (1.0 mi away). Cairo, GA ranks 76th wettest of the 101 cities covered in Georgia.
Month by month in Cairo
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 4.64 | 3,688 | |
| Feb | 3.95 | 3,139 | |
| Mar | 5.19 | 4,125 | |
| Apr | 3.20 | 2,543 | 143 |
| May | 2.56 | 2,035 | 223 |
| Jun | 7.07 | 5,619 | |
| Jul | 5.34 | 4,244 | |
| Aug | 4.58 | 3,640 | |
| Sep | 4.20 | 3,338 | 19 |
| Oct | 3.05 | 2,424 | 162 |
| Nov | 3.24 | 2,575 | |
| Dec | 3.92 | 3,116 |
Jun is the wettest month (7.07 in, 5,619 gal off the roof); May the driest (2.56 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 Cairo
Best fit: one 55-gallon barrel, which delivers about 463 gallons to the garden in a normal year (84.6% of its need).
Before you buy, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Cairo's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 463 | 38,930 |
| 110 gal | 463 | 38,930 |
| 165 gal | 463 | 38,930 |
| 275 gal | 463 | 38,930 |
| 550 gal | 463 | 38,930 |
| 1,000 gal | 463 | 38,930 |
| 1,500 gal | 463 | 38,930 |
| 2,500 gal | 463 | 38,930 |
| 5,000 gal | 463 | 38,930 |
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 Georgia?
Legal. Outdoor irrigation use is unrestricted; indoor non-potable systems must follow Appendix I 'Rainwater Recycling Systems' of the Georgia amendments to the state plumbing code. No state storage cap; potable use depends on local rules.
Checked against the current source on 2026-11-06. Source