Arizona volcanic activity risk
Coconino County has the highest volcanic activity risk in Arizona, scoring 85.7 out of 100 — rated "Relatively Low" by FEMA's National Risk Index.
| # | County | NRI score | Rating |
|---|---|---|---|
| 1 | Coconino County | 85.7 | Relatively Low |
| 2 | Mohave County | 60.9 | Very Low |
| 3 | Yuma County | 59.9 | Very Low |
| 4 | Apache County | 57.3 | Very Low |
| 5 | Yavapai County | 57 | Very Low |
| 6 | Navajo County | 53.7 | Very Low |
| 7 | La Paz County | 42.7 | Very Low |
| 8 | Greenlee County | 12.7 | Very Low |
| 9 | Gila County | 9.1 | Very Low |
Source: FEMA National Risk Index v1.20.0, December 2025. Scores are 0–100 percentile rankings among all US counties. See the methodology page for definitions. Download the full CSV for all counties.
Volcanic Activity risk nationally:
Other hazard risks in Arizona:
Frequently asked questions
What is the highest volcanic activity risk county in Arizona?
Coconino County, AZ has the highest volcanic activity risk in Arizona, with a FEMA National Risk Index score of 85.7 out of 100 (rated "Relatively Low").
What causes volcanic activity risk in Arizona?
Volcanic activity risk reflects expected losses from lava flows, tephra fall, lahars (volcanic mudflows), and volcanic gases. The highest-risk counties are in Washington (Mt. Rainier), Oregon (Mt. Hood), and Hawaii (Kilauea, Mauna Loa). Alaska's Aleutian chain contains many active volcanoes affecting nearby communities and trans-Pacific air traffic. Volcanic ashfall events are reported at forecast-zone level in NOAA Storm Events and are not included in county-level counts.