Minneapolis, MN rainwater: 26,459 gallons off a roof
How much rain a roof in Minneapolis, MN collects
26,459gallons a year
That is a 1,500 sq ft asphalt roof under Minneapolis, MN's normal 33.3 inches of rain, about 795 gallons for every inch that falls.
In Minneapolis, MN 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 Minneapolis 0.4 Ne station (0.4 mi away). Minneapolis, MN ranks 35th wettest of the 103 cities covered in Minnesota.
Month by month in Minneapolis
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.80 | 636 | |
| Feb | 0.90 | 715 | |
| Mar | 1.60 | 1,272 | |
| Apr | 3.34 | 2,655 | 126 |
| May | 4.33 | 3,442 | 2 |
| Jun | 4.65 | 3,696 | |
| Jul | 4.44 | 3,529 | |
| Aug | 4.36 | 3,465 | |
| Sep | 3.17 | 2,520 | 147 |
| Oct | 2.92 | 2,321 | 178 |
| Nov | 1.57 | 1,248 | |
| Dec | 1.21 | 962 |
Jun is the wettest month (4.65 in, 3,696 gal off the roof); Jan the driest (0.80 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 Minneapolis
Best fit: one 55-gallon barrel, which delivers about 360 gallons to the garden in a normal year (79.3% 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 Minneapolis's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 360 | 25,094 |
| 110 gal | 360 | 25,094 |
| 165 gal | 360 | 25,094 |
| 275 gal | 360 | 25,094 |
| 550 gal | 360 | 25,094 |
| 1,000 gal | 360 | 25,094 |
| 1,500 gal | 360 | 25,094 |
| 2,500 gal | 360 | 25,094 |
| 5,000 gal | 360 | 25,094 |
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 Minnesota?
No statewide rainwater harvesting regulations; check county for local incentives
From the 2015 (Pacific Northwest National Laboratory report 24347); not yet re-checked against current law, so check with your state water agency before building anything large. Source