Blaine, MN rainwater: 22,906 gallons off a roof

Rainwater from a roof in Blaine, MN

22,906gallons a year

That is a 1,500 sq ft asphalt roof under Blaine, MN's normal 28.8 inches of rain, about 795 gallons for every inch that falls.

In Blaine, 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 Andover 1n station (7.1 mi away). Blaine, MN ranks 94th wettest of the 103 cities covered in Minnesota.

Month by month in Blaine

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	0.57	453
Feb	0.83	660
Mar	1.44	1,145
Apr	2.94	2,337	176
May	3.57	2,837	97
Jun	3.80	3,020	69
Jul	4.46	3,545
Aug	3.60	2,861	94
Sep	2.53	2,011	227
Oct	2.69	2,138	207
Nov	1.38	1,097
Dec	1.01	803

Jul is the wettest month (4.46 in, 3,545 gal off the roof); Jan the driest (0.57 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 Blaine?

Best fit: one 55-gallon barrel, which delivers about 704 gallons to the garden in a normal year (81.0% 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 Blaine's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	704	21,303
110 gal	704	21,303
165 gal	704	21,303
275 gal	704	21,303
550 gal	704	21,303
1,000 gal	704	21,303
1,500 gal	704	21,303
2,500 gal	704	21,303
5,000 gal	704	21,303

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