*Our Storm Impact Scale has been updated since this story was published. For the latest storm impact scale, click here.
You may have noticed on the First Alert5 7 day forecasts an "impact" numbered 1-5. This is the Storm Impact Scale or SIS for short.
News 5 developed the SIS to categorize the severity of an incoming weather event, allowing you to gauge how it will affect your plans.
We have put together a guide so you can learn what conditions merit each impact number, any time of year.
We will categorize this per fall/winter and spring/summer to gauge cold weather or warm weather events. But as we know in Colorado, snow and thunderstorms can extend outside of these seasonal categories, so take this with a grain of salt.
Impact 1
General: Don't cancel your plans, impacts will be minor.
Fall/Winter: Snow accumulations less than 2 inches. Slick roads are possible.
Spring/Summer: Minor showers with minimal lightning.
Impact 2
General: Outdoor plans could be impacted.
Fall/Winter: Snow accumulations 2-4 inches. Icy and snow-packed roads likely.
Spring/Summer: Moderate to heavy rain showers. Minor flooding and frequent lightning possible.
Impact 3
General: Make alternate plans for outdoor activities and travel.
Fall/Winter: Snow accumulations 4-8 inches. Schools may close and travel will be difficult.
Spring/Summer: Severe thunderstorms possible including hail 1 inch or larger and winds gusts over 58 mph. Flooding is possible.
Year-Round: Wind gusts 40-50 mph
Impact 4
General: Stay indoors if you can.
Fall/Winter: Snow accumulations 8-12 inches. Schools and businesses closed. Blizzard conditions are possible.
Spring/Summer: Several severe, damaging thunderstorms expected with large hail, strong winds, flooding, and/or isolated tornadoes possible.
Year-Round: Wind gusts 50-70 mph
Impact 5
General: Dangerous storm, remain sheltered.
Fall/Winter: Snow accumulations over 1 foot. Blizzard conditions expected. Travel becomes impossible. Power outages expected.
Spring/Summer: Major, widespread severe weather. Very large hail, damaging wind or tornadoes likely, and flooding expected.
Year-Round: Wind gusts 70+ mph
