Monroe, MI rainwater: 27,977 gallons off a roof

How much rain a roof in Monroe, MI collects

27,977gallons a year

That is a 1,500 sq ft asphalt roof under Monroe, MI's normal 35.2 inches of rain, about 795 gallons for every inch that falls.

In Monroe, MI 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 Monroe 3.0 S station (3.0 mi away). Monroe, MI ranks 28th wettest of the 90 cities covered in Michigan.

Month by month in Monroe

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	2.30	1,828
Feb	2.02	1,606
Mar	2.80	2,225
Apr	3.32	2,639	128
May	3.88	3,084	59
Jun	3.65	2,901	87
Jul	3.35	2,663	125
Aug	3.55	2,822	100
Sep	2.86	2,273	186
Oct	2.61	2,074	217
Nov	2.71	2,154
Dec	2.15	1,709

May is the wettest month (3.88 in, 3,084 gal off the roof); Feb the driest (2.02 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 Monroe?

Best fit: one 55-gallon barrel, which delivers about 711 gallons to the garden in a normal year (78.9% 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 Monroe's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	711	26,126
110 gal	711	26,126
165 gal	711	26,126
275 gal	711	26,126
550 gal	711	26,126
1,000 gal	711	26,126
1,500 gal	711	26,126
2,500 gal	711	26,126
5,000 gal	711	26,126

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 Michigan?

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