St. Michael, MN rainwater: 25,911 gallons off a roof
St. Michael, MN: gallons off the roof each year
25,911gallons a year
That is a 1,500 sq ft asphalt roof under St. Michael, MN's normal 32.6 inches of rain, about 795 gallons for every inch that falls.
In St. Michael, 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 Saint Michael 1.3 E station (1.2 mi away). St. Michael, MN ranks 62nd wettest of the 103 cities covered in Minnesota.
Month by month in St. Michael
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.90 | 715 | |
| Feb | 0.93 | 739 | |
| Mar | 1.75 | 1,391 | |
| Apr | 2.88 | 2,289 | 183 |
| May | 4.21 | 3,346 | 17 |
| Jun | 4.41 | 3,505 | |
| Jul | 4.19 | 3,330 | 20 |
| Aug | 4.71 | 3,744 | |
| Sep | 3.13 | 2,488 | 152 |
| Oct | 2.58 | 2,051 | 221 |
| Nov | 1.67 | 1,327 | |
| Dec | 1.24 | 986 |
Aug is the wettest month (4.71 in, 3,744 gal off the roof); Jan the driest (0.90 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 St. Michael
Best fit: one 55-gallon barrel, which delivers about 501 gallons to the garden in a normal year (84.4% 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. Michael's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 501 | 24,599 |
| 110 gal | 501 | 24,599 |
| 165 gal | 501 | 24,599 |
| 275 gal | 501 | 24,599 |
| 550 gal | 501 | 24,599 |
| 1,000 gal | 501 | 24,599 |
| 1,500 gal | 501 | 24,599 |
| 2,500 gal | 501 | 24,599 |
| 5,000 gal | 501 | 24,599 |
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