Port Huron, MI rainwater: 27,715 gallons off a roof
Port Huron, MI: gallons off the roof each year
27,715gallons a year
That is a 1,500 sq ft asphalt roof under Port Huron, MI's normal 34.9 inches of rain, about 795 gallons for every inch that falls.
In Port Huron, 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 Port Huron station (1.5 mi away). Port Huron, MI ranks 42nd wettest of the 90 cities covered in Michigan.
Month by month in Port Huron
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 2.48 | 1,971 | |
| Feb | 2.06 | 1,637 | |
| Mar | 2.21 | 1,757 | |
| Apr | 3.15 | 2,504 | 150 |
| May | 3.53 | 2,806 | 102 |
| Jun | 3.62 | 2,877 | 91 |
| Jul | 3.25 | 2,583 | 137 |
| Aug | 3.14 | 2,496 | 151 |
| Sep | 3.32 | 2,639 | 128 |
| Oct | 3.13 | 2,488 | 152 |
| Nov | 2.81 | 2,233 | |
| Dec | 2.17 | 1,725 |
Jun is the wettest month (3.62 in, 2,877 gal off the roof); Feb the driest (2.06 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 Port Huron
Best fit: one 55-gallon barrel, which delivers about 699 gallons to the garden in a normal year (76.7% of its need).
If you buy one, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Port Huron's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 699 | 25,830 |
| 110 gal | 699 | 25,830 |
| 165 gal | 699 | 25,830 |
| 275 gal | 699 | 25,830 |
| 550 gal | 699 | 25,830 |
| 1,000 gal | 699 | 25,830 |
| 1,500 gal | 699 | 25,830 |
| 2,500 gal | 699 | 25,830 |
| 5,000 gal | 699 | 25,830 |
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