Jerome, ID rainwater: 8,306 gallons off a roof
How much rain a roof in Jerome, ID collects
8,306gallons a year
That is a 1,500 sq ft asphalt roof under Jerome, ID's normal 10.5 inches of rain, about 795 gallons for every inch that falls.
Jerome, ID's rain arrives in a wet season and stops, so storage is what matters. It takes a cistern of 1,000 gallons to carry spring rain into the dry months.
Rainfall: NOAA 1991-2020 climate normals, the Jerome station (1.0 mi away). Jerome, ID ranks 24th wettest of the 26 cities covered in Idaho.
Month by month in Jerome
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.38 | 1,097 | |
| Feb | 0.82 | 652 | |
| Mar | 1.07 | 850 | |
| Apr | 1.02 | 811 | 415 |
| May | 1.32 | 1,049 | 378 |
| Jun | 0.61 | 485 | 466 |
| Jul | 0.13 | 103 | 526 |
| Aug | 0.25 | 199 | 511 |
| Sep | 0.43 | 342 | 489 |
| Oct | 0.89 | 707 | 431 |
| Nov | 1.03 | 819 | |
| Dec | 1.50 | 1,192 |
Dec is the wettest month (1.50 in, 1,192 gal off the roof); Jul the driest (0.13 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 Jerome?
Best fit: a 1,000-gallon cistern, which delivers about 2,829 gallons to the garden in a normal year (87.9% of its need).
Before you buy, ask about a rebate first: cistern-sized storage costs real money, and a buried or tall tank may need a permit. Place it where a full tank (about 8.3 lb a gallon) sits on firm, level ground.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 812 | 6,881 |
| 110 gal | 1,480 | 6,213 |
| 165 gal | 1,785 | 5,907 |
| 275 gal | 2,081 | 5,611 |
| 550 gal | 2,379 | 5,314 |
| 1,000 gal | 2,829 | 4,864 |
| 1,500 gal | 3,019 | 4,673 |
| 2,500 gal | 3,019 | 4,673 |
| 5,000 gal | 3,019 | 4,347 |
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 Idaho?
Allowed through a legal clarification made by the Office of the Attorney General
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