Fort Collins, CO rainwater: 13,043 gallons off a roof
Fort Collins, CO: gallons off the roof each year
13,043gallons a year
That is a 1,500 sq ft asphalt roof under Fort Collins, CO's normal 16.4 inches of rain, about 795 gallons for every inch that falls.
In Fort Collins, CO 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 Fort Collins 0.3 Sse station (0.2 mi away). Fort Collins, CO ranks 28th wettest of the 53 cities covered in Colorado.
Month by month in Fort Collins
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.46 | 366 | |
| Feb | 0.52 | 413 | |
| Mar | 1.29 | 1,025 | |
| Apr | 2.07 | 1,645 | 284 |
| May | 2.86 | 2,273 | 186 |
| Jun | 1.95 | 1,550 | 299 |
| Jul | 1.68 | 1,335 | 333 |
| Aug | 1.53 | 1,216 | 352 |
| Sep | 1.44 | 1,145 | 363 |
| Oct | 1.30 | 1,033 | 380 |
| Nov | 0.77 | 612 | |
| Dec | 0.54 | 429 |
May is the wettest month (2.86 in, 2,273 gal off the roof); Jan the driest (0.46 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 Fort Collins
Best fit: 2 linked 55-gallon barrels, which delivers about 1,908 gallons to the garden in a normal year (86.9% 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 Fort Collins's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,367 | 11,060 |
| 110 gal | 1,908 | 10,520 |
| 165 gal (over cap) | 1,915 | 10,513 |
| 275 gal (over cap) | 1,915 | 10,513 |
| 550 gal (over cap) | 1,915 | 10,513 |
| 1,000 gal (over cap) | 1,915 | 10,513 |
| 1,500 gal (over cap) | 1,915 | 10,513 |
| 2,500 gal (over cap) | 1,915 | 10,513 |
| 5,000 gal (over cap) | 1,915 | 10,513 |
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 Colorado?
Most households may use rain barrels: a maximum of two rain barrels with a combined storage of 110 gallons or less per household, rooftop runoff only, used outdoors on the same property (HB16-1005). Larger rooftop collection only for qualifying well-permit holders (SB09-080) or pilot projects (HB09-1129).
Checked against the current source on 2026-11-06. Source