Fargo, ND rainwater: 19,616 gallons off a roof

How much rain a roof in Fargo, ND collects

19,616gallons a year

That is a 1,500 sq ft asphalt roof under Fargo, ND's normal 24.7 inches of rain, about 795 gallons for every inch that falls.

In Fargo, ND 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 Fargo 1.2 Ese station (1.8 mi away). Fargo, ND ranks 2nd wettest of the 9 cities covered in North Dakota.

Month by month in Fargo

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	0.68	540
Feb	0.65	517
Mar	1.20	954
Apr	1.45	1,152	362
May	3.46	2,750	111
Jun	4.37	3,473
Jul	3.42	2,718	116
Aug	2.52	2,003	228
Sep	2.80	2,225	193
Oct	2.42	1,923	241
Nov	0.88	699
Dec	0.83	660

Jun is the wettest month (4.37 in, 3,473 gal off the roof); Feb the driest (0.65 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 Fargo?

Best fit: one 55-gallon barrel, which delivers about 975 gallons to the garden in a normal year (78.0% 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 Fargo's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	975	17,861
110 gal	1,051	17,785
165 gal	1,051	17,785
275 gal	1,051	17,785
550 gal	1,051	17,785
1,000 gal	1,051	17,785
1,500 gal	1,051	17,785
2,500 gal	1,051	17,785
5,000 gal	1,051	17,785

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 North Dakota?

No rainwater harvesting regulations

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