Key West, FL rainwater: 36,950 gallons off a roof
Rainwater from a roof in Key West, FL
36,950gallons a year
That is a 1,500 sq ft asphalt roof under Key West, FL's normal 46.5 inches of rain, about 795 gallons for every inch that falls.
In Key West, 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 Key West 0.5 Sw station (0.6 mi away). Key West, FL ranks 170th wettest of the 173 cities covered in Florida.
Month by month in Key West
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.85 | 1,470 | |
| Feb | 1.89 | 1,502 | |
| Mar | 1.62 | 1,288 | |
| Apr | 2.37 | 1,884 | 247 |
| May | 3.95 | 3,139 | 50 |
| Jun | 5.33 | 4,236 | |
| Jul | 5.31 | 4,220 | |
| Aug | 6.20 | 4,928 | |
| Sep | 8.01 | 6,366 | |
| Oct | 5.32 | 4,228 | |
| Nov | 2.48 | 1,971 | |
| Dec | 2.16 | 1,717 |
Sep is the wettest month (8.01 in, 6,366 gal off the roof); Mar the driest (1.62 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
What size rain barrel for Key West
Best fit: 2 linked 55-gallon barrels, which delivers about 264 gallons to the garden in a normal year (89.0% of its need).
If you buy one, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Key West's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 226 | 35,795 |
| 110 gal | 264 | 35,756 |
| 165 gal | 264 | 35,756 |
| 275 gal | 264 | 35,756 |
| 550 gal | 264 | 35,756 |
| 1,000 gal | 264 | 35,756 |
| 1,500 gal | 264 | 35,756 |
| 2,500 gal | 264 | 35,756 |
| 5,000 gal | 264 | 35,756 |
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