* Actual air temperature: Extremely hot or cold temperatures are a major factor. However, the threshold varies widely depending on the region and the age of the students. Younger children are more vulnerable to extreme temperatures.
* Wind chill: Cold wind makes the temperature feel much colder and can lead to hypothermia.
* Heat index: High humidity combined with high temperatures creates a heat index that can make it feel even hotter and more dangerous.
* Icy or snowy conditions: These make it dangerous for students and staff to travel to and from school.
* School district policies: Each school district has its own policies about closing school due to weather. These policies may be based on temperature thresholds, but also consider other safety factors.
* Transportation considerations: If school buses can't safely operate due to weather conditions, schools may close.
In short, there's no magic number. Parents should check with their local school district or monitor local news for announcements about school closures due to weather.