Winter storm events on GEO use an intensity-based Exposure Layer that focuses on areas where conditions are genuinely likely to cause insured loss. This article explains how MIS assesses winter storm intensity and what the layer shows.
[SCREENSHOT: Winter storm event on GEO showing the intensity grid across the affected region]
How MIS assesses winter storm intensity
Winter storms present a different challenge from wind or flood events — widespread cold and snow doesn't automatically mean widespread insured damage. MIS deliberately avoids flagging broad areas as impacted unless the conditions meet thresholds likely to drive real claims activity.
The Exposure Layer for winter storms is derived from three drivers of impact, measured across the full duration of the event:
Driver | How it's measured |
Temperature | The lowest temperature recorded for that area over the event |
Power Outages | The highest percentage of customers affected at any point during the event |
Snow Accumulation | Total accumulation over the event duration |
Intensity classifications
The overall intensity classification reflects how these three factors combine spatially. Minimal and Low intensity assessments are not used as standard for winter storm events — MIS only publishes cells at Moderate or above, to avoid overstating the impacted area.
Intensity | Temperature (°C) | Power Outage | Snow Accumulation |
Minimal | > 0 | < 5% | 5–10 cm |
Low | 0 to −5 | 6–10% | 10–20 cm |
Moderate | −5 to −10 | 11–30% | 20–30 cm |
High | −10 to −20 | 31–50% | 30–50 cm |
Severe | < −20 | > 50% | > 50 cm |
Important: If temperatures do not fall below 0°C, the intensity cannot exceed Low regardless of snowfall or power outage levels. This threshold reflects MIS's intent to highlight areas of genuine concern rather than broadly mapping meteorological conditions unlikely to cause loss.
What winter storm reports typically include
Most winter storm events include an Exposure Layer with intensity grid and a Power Outage layer updated daily. A Claims Layer is unlikely for winter storms — damage tends to be dispersed and difficult to assess at grid level. Imagery is also rare for winter storm events.
FAQ
Why is such a large geographic area not shown on the layer even though it was affected by the storm?
MIS focuses on areas where conditions reached thresholds linked to insured loss. Areas with cold or snow that didn't reach those thresholds are intentionally excluded.
Will there be a Claims Layer for winter storms?
Rarely. Winter storm damage is typically dispersed across a wide area without concentrated structural damage of the kind that supports a grid-based claims assessment. MIS will publish one if sufficient data exists.
What does the Power Outage layer show for winter storms?
It shows the percentage of utility customers without power by county, updated daily. This is often the most useful proxy for insured loss in a winter storm event.
Related articles
[Understanding GEO Layers]
[Year Long Reports]
[Our Response Timelines]