Chester County
Pennsylvania — Natural Disaster Risk Assessment
MediumComposite Risk Score
National percentile: 92th
Chester County faces medium composite natural disaster risk (NRI Risk Index score 91.9, 92th national percentile), driven primarily by drought and winter weather exposure. Expected annual loss across all 18 hazard types is $173M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Top Hazards
All 18 Hazard Risks
| Drought | High | 4.93 / yr | $10M |
| Winter Weather | Very High | 12.13 / yr | $2M |
| Heat Wave | Medium | 9.18 / yr | $11M |
| Strong Wind | High | 7.21 / yr | $5M |
| Riverine Flood | High | 5.46 / yr | $106M |
| Lightning | High | 35.75 / yr | $2M |
| Earthquake | Medium | 0.00 / yr | $8M |
| Hurricane | Medium | 0.08 / yr | $10M |
| Tornado | Medium | 0.45 / yr | $10M |
| Ice Storm | High | 1.33 / yr | $993K |
| Cold Wave | Medium | 0.92 / yr | $8M |
| Landslide | Low | 0.66 / yr | $20K |
| Hail | Low | 2.76 / yr | $618K |
| Wildfire | Very Low | 0.00 / yr | $23K |
| Avalanche | Very Low | 0.00 / yr | $0 |
| Coastal Flood | Very Low | 0.01 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Frequently Asked Questions
What is the overall natural disaster risk for Chester County?
Chester County has a composite FEMA National Risk Index score of 91.9 out of 100, placing it in the Medium category and the 92th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Chester County?
The three highest-rated hazards are Drought (High, $10M EAL), Winter Weather (Very High, $2M EAL), Heat Wave (Medium, $11M EAL). These account for most of the county's expected annual losses.
How does Chester County compare to other Pennsylvania counties?
Chester County ranks #9 of 67 Pennsylvania counties for overall natural disaster risk, with a medium rating.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. Chester County's $173M EAL is a statistical average, not a guarantee for any specific year or address.