St. Petersburg, FL rainwater: 41,711 gallons off a roof
How much rain a roof in St. Petersburg, FL collects
41,711gallons a year
That is a 1,500 sq ft asphalt roof under St. Petersburg, FL's normal 52.5 inches of rain, about 795 gallons for every inch that falls.
In St. Petersburg, FL 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 St Petersburg station (1.1 mi away). St. Petersburg, FL ranks 139th wettest of the 173 cities covered in Florida.
Month by month in St. Petersburg
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 2.97 | 2,361 | |
| Feb | 2.17 | 1,725 | |
| Mar | 2.86 | 2,273 | |
| Apr | 2.60 | 2,066 | 218 |
| May | 2.54 | 2,019 | 226 |
| Jun | 7.18 | 5,707 | |
| Jul | 8.35 | 6,637 | |
| Aug | 9.33 | 7,416 | |
| Sep | 7.51 | 5,969 | |
| Oct | 2.52 | 2,003 | 228 |
| Nov | 1.61 | 1,280 | |
| Dec | 2.84 | 2,257 |
Aug is the wettest month (9.33 in, 7,416 gal off the roof); Nov the driest (1.61 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
Barrel or cistern in St. Petersburg?
Best fit: one 55-gallon barrel, which delivers about 546 gallons to the garden in a normal year (81.3% 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 St. Petersburg's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 546 | 40,115 |
| 110 gal | 599 | 40,062 |
| 165 gal | 599 | 40,062 |
| 275 gal | 599 | 40,062 |
| 550 gal | 599 | 40,062 |
| 1,000 gal | 599 | 40,062 |
| 1,500 gal | 599 | 40,062 |
| 2,500 gal | 599 | 40,062 |
| 5,000 gal | 599 | 40,062 |
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 Florida?
Legal. Florida approves onsite non-potable use of rainwater for landscape irrigation, vehicle washing, filling pools and fountains and, in some local jurisdictions, toilet/urinal flushing (Florida Plumbing Code). No state storage cap or registration for non-potable collection.
Checked against the current source on 2026-11-06. Source