Arapahoe County, CO Environment & Hazard Risk
Relatively Moderate natural hazard risk, led by hail. 1,358 storm events since 1996.
- Expected yearly loss
- $172M
- Relatively Moderate nationally
- Storm events since 1996
- 1,358
- Most often hail
- Flood insurance policies
- 677
- 0.3% of homes
- Hurricanes nearby
- 0
- Since 1851
Natural hazard risk
FEMA National Risk Index, December 2025
Overall risk
Relatively Moderate
Score 93.8 of 100
Social vulnerability
Very Low
Score 18.4 of 100
Community resilience
Relatively Moderate
Score 49.4 of 100
Community resilience runs the other way: a higher rating means a community can recover faster.
Building value exposed: $120B · Agriculture value exposed: $34.34M · Risk-adjusted yearly loss: $150M
Risk by hazard
- HailVery High$63.98M/yr expected annual loss, about 8.6 events a year
- LightningVery High$4.03M/yr expected annual loss, about 52 events a year
- TornadoRelatively High$22.36M/yr expected annual loss, about 1.1 events a year
- Strong windRelatively High$3.72M/yr expected annual loss, about 1.4 events a year
- Cold waveRelatively High$9.4M/yr expected annual loss, about 1.6 events a year
- Winter weatherRelatively High$519K/yr expected annual loss, about 13 events a year
- EarthquakeRelatively Low$3.52M/yr expected annual loss, about once every 1,522 years
- WildfireRelatively Low$802K/yr expected annual loss, about once every 671 years
- Volcanic activityVery Low$155/yr expected annual loss, about once every 10,000 years
- Heat waveRelatively Low$1.03M/yr expected annual loss, about once every 1 year
- LandslideVery Low$1,652/yr expected annual loss, about once every 7 years
- DroughtRelatively Low$118K/yr expected annual loss, about 29 events a year
- Ice stormVery Low$7,305/yr expected annual loss, about once every 38 years
Bars show the national percentile score (0 to 100) for each hazard. Dollar figures are expected annual losses to buildings, people and crops. Not rated here: avalanche, coastal flooding, hurricane, riverine flooding, tsunami.
Flood risk and insurance
National Flood Insurance Program and FEMA flood maps
Check the flood zone for an address
- Homes with flood insurance
- 677 of 199,030 (0.3%)
- Homes in high-risk flood zones
- 397
- Insured in high-risk zones
- 192 (48%)
- Flood claims since 1978
- 207
- Claims paid since 1978
- $1.04M
Flood claims paid per year
- Late summer storms$247K · 30 claims
- Flooding$12.48K · 3 claims
Storm history
Since 1996: 1,358 events, 14 deaths, $1.12B in damage
- Hail460
- Winter Weather176 · 5 deaths
- Winter Storm161
- High Wind144
- Thunderstorm Wind110
- Heavy Snow80
- Blizzard50 · 2 deaths
- Tornado49
- Flash Flood36 · 2 deaths
- Lightning30
Events per year
100 tornadoes on record (EF0 17, EF1 5, EF2 1, F0 46, F1 27, F2 1).
Most damaging storms
Since 1996, ranked by deaths, injuries and damage
- Hail3" hail06/19/2018
Englewood, Arapahoe County
$276M damage
What happened
The property estimate value was the total storm damage summary for the event.
- Hail1.75" hail09/29/2014
Centennial Airport, Arapahoe County
$213M damage
What happened
A storm system that moved through the area produced large hail, up to golfball size, and street flooding in parts of the metro area then spread east into the plains. The hailstorm was the most costly of the summer season with with insured losses topping $213.3 million, according to the Rocky Mountain Insurance Information Association.|Insurance claims included 29,297 automobile claims worth more than $87.2 million and 14,287 property claims for $126 million, ranking the storm as the eighth most expensive to hit the state. The storm also caused multiple accidents. A semi became detached from a trailer, blocking traffic on westbound Interstate 70 west of Tower Road. Downed power poles blocked a roadway on CO 79 near Bennett, at mile marker 10. In addition to the damaging winds, the storms produced large hail, from nickel to golfball size. The intense thunderstorm winds also downed trees near Fort Morgan. Flash flooding was reported over parts of northern Washington County. The combination of flash flooding and an accident involving a semi-trailer forced the closure of CO 61 for a several hours.
- Hail2.5" hail06/07/2012
Byers, Arapahoe County
$161M damage
What happened
Severe thunderstorms brought damaging wind and hail, heavy rain, along several tornadoes, one of which was rated an EF-2. The storms produced hail from 1.5 to 2.75 inches in diameter. In addition to the large hail, heavy rainfall from 1 to 2 inches also accompanied the storms. The combination of hail and heavy rain caused extensive street flooding across Aurora, Castle Rock, Centennial, Cherry Creek, Englewood, South Denver, Highlands Ranch, Lakewood and Littleton. The hail was reportedly knee deep in several areas making roads impassable. As a result, snow plows had to be summoned to clear the streets. In Castle Rock, a King Soopers supermarket sustained extensive damage when roof partially collapsed under the weight of the hail. Total property damage estimates along the Front Range for the 6th and 7th combined was 321.1 million dollars. ||A tornado touched down in Elbert County Thursday evening, June 7th, producing considerable damage to homes and several farm buildings in south central Elbert County. The tornado was rated an EF-2 at it's strongest point near Elbert County Road 82 and just west of Elbert County Road 97. The tornado initially touched down...
- Hail3" hail06/07/2009
Aurora Cherry Creek, Arapahoe County
$161M damage
What happened
Severe thunderstorms in Denver and the surrounding metropolitan area produced five tornadoes, large hail and damaging thunderstorm winds. The strongest of the tornadoes touched down near Southlands Mall, in southeast Aurora. Two men were injured, one seriously. Overall the damage was rated mild to moderate, which translated to an EF1 rating. Four other tornadoes touched down, two of which caused minor damage. Another EF1 tornado damaged a home, several outbuildings, and injured some horses in unincorporated Elbert County.||In addition to the tornadoes, large hail from 1 to 3 inches in diameter was observed. In parts of Aurora and Centennial, thunderstorm winds blew down power lines and caused electrical outages. Approximately 8,000 homes and businesses were left without power for nearly two hours. Most of the damage consisted of broken windows and roofs. This day was the first in a series of eight to cause damage along the Urban Corridor. Damage to homes and property along the Front Range totalled $161 million during the 8-day span, making it the state's fifth highest insurance loss. The majority of the property damage was caused by hail; 21,000 automobile claims...
- Hail1" hail06/07/2012
South Glenn, Arapahoe County
$160M damage
What happened
Severe thunderstorms broke late in the evening, striking areas hardest from Denver southward. Locations impacted by the storms included but were not limited to: Aurora, Castle Rock, Centennial, Highlands Ranch, Lone Tree, Parker, Surrey Ridge. The storms produced a barrage of large hail, damaging straight line winds, flash flooding and several short lived tornadoes. The hail ranged in size from 1 to 2 inches in diameter, and caused extensive damage to homes and automobiles. The hail inundated the roadways with several inches of hail in Douglas County. Consequently, snow plows had to be called out to clear the roadways. One tornado that touched down near Grover in Weld County ripped a tree from the ground and tossed it approximately twenty feet. ||The combination of torrential hail and heavy rain produced flash flooding in parts of Elbert, Douglas and Arapahoe Counties, as thunderstorms brought up to 3.35 inches of rain to some areas within 90 minutes. In Aurora, Picadilly Road was closed from flooding north of 6th Avenue. A water rescue took place on South Gun Club Road in Arapahoe County, where floodwaters were rushing to depth of 3 feet. Flash flooding forced the...
- Hail2" hail10/16/1998
(Bkf)buckley Fld Nas, Arapahoe County
$87.8M damage
What happened
A potent late season hailstorm struck portions of Denver and the surrounding metro area. The storm began dumping torrential hail, mostly pea sized, over portions of Arvada and Wheat Ridge, northwest of Denver. Hail, heaviest near Interstate 70, reportedly piled up to 6 inches deep. Several accidents were attributed, at least in part, to the hailstorm. Snowplows had to be called out to clear several city streets.As the storm moved southeast, into the Denver and Aurora areas, it intensified. Large hail, up to 2 inches in diameter pounded the area. Damage estimates totalled $87.8 million ($27.3 million in homeowner claims and $60.5 million in automobile claims), making this the 7th costliest hailstorm to strike the Denver Metropolitan Area.
Latest storm reports
Newest first
- Thunderstorm Wind53 kt wind07/28/2026
Arapahoe Park, Arapahoe County
- Thunderstorm Wind50 kt wind07/28/2026
Arapahoe Park, Arapahoe County
- Thunderstorm Wind50 kt wind07/28/2026
Arapahoe Park, Arapahoe County
- Thunderstorm Wind57 kt wind07/28/2026
Arapahoe Park, Arapahoe County
- Thunderstorm Wind54 kt wind07/08/2026
Byers, Arapahoe County
- Thunderstorm Wind63 kt wind07/08/2026
Byers, Arapahoe County
- Thunderstorm Wind66 kt wind06/25/2026
Peoria, Arapahoe County
- Hail1.25" hail06/25/2026
Deer Trail, Arapahoe County
Drinking water
30 community water systems serve about 865,342 people. Violations since 2021.
4 systems had health-based violations, such as a contaminant over the legal limit or a missed treatment step. 2 systems had a violation of any kind still open at last report.
- Aurora City ofServes 533,407 · Surface water · Local governmentNo health violations
- East Cherry Creek Valley WsdServes 66,130 · Purchased surface water · Local governmentNo health violations+4 monitoring or reporting
- Englewood City ofServes 59,904 · Surface water · Local government1 health violation+5 monitoring or reporting
- Southgate WsdServes 55,000 · Purchased surface water · Local governmentNo health violations
- Southwest Metropolitan WsdServes 48,648 · Purchased surface water · Local governmentNo health violations
- Arapahoe Cnty WwwaServes 31,000 · Groundwater · PrivateNo health violations
- Platte Canyon WsdServes 19,485 · Purchased surface water · Local governmentNo health violations
- Willows WdServes 19,000 · Purchased surface water · Local governmentNo health violations
Largest systems by population served. Monitoring and reporting violations mean required tests or notices were late or missing, not that the water was unsafe.
Climate
1991-2020 normals at Byers 5 Ene, 10 mi from the county center
Summer highs peak around 90°F in Jul and winter lows bottom out near 14°F in Dec. About 16.3 inches of rain falls in a typical year, with 42.7 inches of snow.
| Month | High | Low | Rain | Snow |
|---|---|---|---|---|
| Jan | 42°F | 14°F | 0.45 in | 6.1 in |
| Feb | 45°F | 16°F | 0.52 in | 6.3 in |
| Mar | 54°F | 25°F | 1.21 in | 7.3 in |
| Apr | 61°F | 32°F | 1.82 in | 5.5 in |
| May | 71°F | 42°F | 2.46 in | 0.7 in |
| Jun | 83°F | 51°F | 1.98 in | - |
| Jul | 90°F | 57°F | 2.56 in | - |
| Aug | 87°F | 56°F | 1.99 in | - |
| Sep | 79°F | 47°F | 1.20 in | 0.9 in |
| Oct | 65°F | 33°F | 0.98 in | 3.8 in |
| Nov | 53°F | 22°F | 0.67 in | 5.9 in |
| Dec | 43°F | 14°F | 0.45 in | 6.2 in |
| Year | 49°F average | 16.3 in | 42.7 in | |
Pollution sites
1 Superfund site and 5 toxic release facilities in Arapahoe County
Superfund sites
- Lowry LandfillFinalUnincorporated Arapahoe County
Toxic release facilities
- U.S. Dod Usaf Buckley Sfb Co271 lbs released, Aurora
- Unicircuit Inc46.3 lbs released, Littleton
- Dfa Dairy Brands Fluid LLC D/B/A Meadow Gold Dairy5 lbs released, Englewood
- Brannan Ready Mix - South Ready Mixunder 1 lb released, Englewood
- American Stainless Steel Corp0 lbs released, Englewood
Total: 323 lbs in 2024, 55.3 lbs to air.
Superfund sitesToxic release facilitiesEPA inspections and enforcementAir toxics cancer risk18 historic places
Frequently asked questions
- How risky is Arapahoe County for natural disasters?
- FEMA rates Arapahoe County relatively moderate for overall natural hazard risk, with expected losses of $172M a year. The highest-rated hazards are hail (very high), lightning (very high), tornado (relatively high).
- What storms are most common in Arapahoe County?
- Since 1996, NOAA recorded 1,358 storm events affecting Arapahoe County, most often hail (460), winter weather (176), winter storm (161).
- How many tornadoes have hit Arapahoe County?
- 100 tornadoes have been recorded in Arapahoe County since 1950.
- How many homes in Arapahoe County have flood insurance?
- 677 residential flood insurance policies are in force in Arapahoe County, covering about 0.3% of homes. The program has paid $1.04M on 207 claims here since 1978.
- What is the weather like in Arapahoe County?
- At Byers 5 Ene, average highs reach 90°F in Jul and lows fall to 14°F in Dec, with 16.3 inches of rain a year (1991-2020 normals).
Source: FEMA (National Risk Index, NFIP), NOAA (Storm Events, HURDAT2, Climate Normals), EPA · Last updated 08/01/2026 · Storm counts include events in forecast zones that touch the county. This product uses the FEMA OpenFEMA API, but is not endorsed by FEMA.