When the National Weather Service issues a winter weather alert, how likely is it that schools will close? Our analysis of 10,000+ weather alerts shows the exact correlation between different types of NWS warnings and school closures. This data has been instrumental in refining our prediction algorithm to provide more accurate snow day forecasts.
Alert Types and School Closure Correlation
Our research has revealed clear patterns in how different alert types correlate with school closure decisions:
| Alert Type | Closure Rate | Delay Rate | No Impact Rate |
|---|---|---|---|
| Ice Storm Warning | 93% | 6% | 1% |
| Blizzard Warning | 89% | 9% | 2% |
| Winter Storm Warning | 78% | 17% | 5% |
| Winter Weather Advisory | 42% | 38% | 20% |
| Freezing Rain Advisory | 57% | 35% | 8% |
| Wind Chill Advisory | 31% | 45% | 24% |
| Wind Chill Warning | 76% | 21% | 3% |
As the data shows, Ice Storm Warnings have the highest correlation with school closures at 93%, followed by Blizzard Warnings at 89%. Winter Weather Advisories, which are more common but indicate less severe conditions, result in closures only 42% of the time.
Timing Matters: When Alerts Are Issued
The timing of weather alerts significantly impacts closure decisions:
- Alerts issued before 3 PM the previous day result in 15% more closures than those issued later, as they give administrators more time to prepare.
- Alerts that expire before 10 AM are 27% less likely to result in closures than those that remain in effect through the morning commute.
- Alerts issued or upgraded overnight (between 10 PM and 5 AM) create the most challenging decision scenarios and show the most variability in outcomes.
Regional Variations in Alert Response
Our analysis revealed significant regional differences in how schools respond to the same alert types:
- Northern regions: Winter Weather Advisories result in closures only 28% of the time, compared to 67% in southern regions less accustomed to winter weather.
- Urban vs. Rural: Rural districts are 35% more likely to close in response to the same alert type compared to urban districts with shorter bus routes and better road maintenance.
- Coastal areas: Winter Storm Warnings in coastal regions result in closures 84% of the time, higher than the national average, due to the often mixed precipitation types that can include more ice.
Alert Language and Specificity
The specific language used in alerts also impacts closure decisions:
- Alerts that specifically mention "difficult or impossible travel conditions" increase closure probability by 23%.
- Alerts that include specific snowfall amounts above 6 inches correlate with 31% more closures than those with more general wording.
- Alerts that mention "life-threatening" conditions result in closures 92% of the time, regardless of the alert type.
How We Use This Data
We've created a precise probability table that shows the likelihood of school closures based on alert type, timing, and local factors. This data powers our prediction engine in several ways:
- Our algorithm continuously monitors NWS alerts for your area and adjusts closure probabilities in real-time.
- We combine alert data with local school district history to create customized prediction models for each district.
- When multiple alerts are issued (such as a Winter Storm Warning followed by a Wind Chill Advisory), our system calculates the compound effect on closure probability.
Understanding the relationship between official weather alerts and school closure decisions has been a key factor in improving our prediction accuracy. By analyzing not just the weather conditions themselves, but how school administrators respond to official alerts about those conditions, we're able to provide more reliable forecasts of when schools are likely to close.