Holyoke, MA rainwater: 35,893 gallons off a roof

How much rain a roof in Holyoke, MA collects

35,893gallons a year

That is a 1,500 sq ft asphalt roof under Holyoke, MA's normal 45.2 inches of rain, about 795 gallons for every inch that falls.

In Holyoke, MA 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 Westfield Barnes Muni Ap station (5.3 mi away). Holyoke, MA ranks 53rd wettest of the 58 cities covered in Massachusetts.

Month by month in Holyoke

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	2.75	2,186
Feb	2.60	2,066
Mar	3.43	2,726
Apr	4.06	3,227	36
May	3.71	2,949	80
Jun	4.37	3,473
Jul	4.15	3,298	25
Aug	3.72	2,957	79
Sep	4.60	3,656
Oct	4.72	3,751
Nov	3.47	2,758
Dec	3.58	2,845

Oct is the wettest month (4.72 in, 3,751 gal off the roof); Feb the driest (2.60 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 Holyoke?

Best fit: one 55-gallon barrel, which delivers about 167 gallons to the garden in a normal year (76.1% 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 Holyoke's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	167	34,526
110 gal	167	34,526
165 gal	167	34,526
275 gal	167	34,526
550 gal	167	34,526
1,000 gal	167	34,526
1,500 gal	167	34,526
2,500 gal	167	34,526
5,000 gal	167	34,526

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 Massachusetts?

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