St. George, UT rainwater: 7,400 gallons off a roof
Rainwater from a roof in St. George, UT
7,400gallons a year
That is a 1,500 sq ft asphalt roof under St. George, UT's normal 9.3 inches of rain, about 795 gallons for every inch that falls.
St. George, UT'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 St George station (3.3 mi away). St. George, UT ranks 64th wettest of the 67 cities covered in Utah.
Month by month in St. George
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.22 | 970 | |
| Feb | 1.38 | 1,097 | |
| Mar | 1.02 | 811 | |
| Apr | 0.66 | 525 | 460 |
| May | 0.33 | 262 | 501 |
| Jun | 0.16 | 127 | 522 |
| Jul | 0.50 | 397 | 480 |
| Aug | 1.07 | 850 | 409 |
| Sep | 0.67 | 533 | 459 |
| Oct | 0.77 | 612 | 446 |
| Nov | 0.67 | 533 | |
| Dec | 0.86 | 684 |
Feb is the wettest month (1.38 in, 1,097 gal off the roof); Jun the driest (0.16 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
What size rain barrel for St. George
Best fit: a 1,000-gallon cistern, which delivers about 3,088 gallons to the garden in a normal year (94.2% of its need).
If you set one up, 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 | 605 | 6,352 |
| 110 gal | 1,198 | 5,759 |
| 165 gal | 1,693 | 5,264 |
| 275 gal | 2,276 | 4,681 |
| 550 gal | 2,638 | 4,319 |
| 1,000 gal | 3,088 | 3,869 |
| 1,500 gal | 3,129 | 3,828 |
| 2,500 gal | 3,129 | 3,828 |
| 5,000 gal (over cap) | 3,129 | 2,656 |
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 Utah?
Up to 2 covered containers of max 100 gal each with no registration; with free registration at the Utah Division of Water Rights, total storage up to 2,500 gal. Use limited to the same parcel where captured.
Checked against the current source on 2026-11-06. Source