Miami, FL rainwater: 45,447 gallons off a roof
How much rain a roof in Miami, FL collects
45,447gallons a year
That is a 1,500 sq ft asphalt roof under Miami, FL's normal 57.2 inches of rain, about 795 gallons for every inch that falls.
In Miami, 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 Miami Beach station (5.1 mi away). Miami, FL ranks 69th wettest of the 173 cities covered in Florida.
Month by month in Miami
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 2.33 | 1,852 | |
| Feb | 2.27 | 1,804 | |
| Mar | 2.47 | 1,963 | |
| Apr | 3.44 | 2,734 | 113 |
| May | 4.94 | 3,926 | |
| Jun | 7.76 | 6,168 | |
| Jul | 5.98 | 4,753 | |
| Aug | 7.51 | 5,969 | |
| Sep | 8.45 | 6,716 | |
| Oct | 6.49 | 5,158 | |
| Nov | 3.29 | 2,615 | |
| Dec | 2.25 | 1,788 |
Sep is the wettest month (8.45 in, 6,716 gal off the roof); Dec the driest (2.25 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 Miami?
Best fit: one 55-gallon barrel, which delivers about 95 gallons to the garden in a normal year (83.7% 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 Miami's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 95 | 44,122 |
| 110 gal | 95 | 44,122 |
| 165 gal | 95 | 44,122 |
| 275 gal | 95 | 44,122 |
| 550 gal | 95 | 44,122 |
| 1,000 gal | 95 | 44,122 |
| 1,500 gal | 95 | 44,122 |
| 2,500 gal | 95 | 44,122 |
| 5,000 gal | 95 | 44,122 |
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