In my days did they cancel school at 6pm the day before a storm when the sky was partly cloudy or clear? Nope.
They cancelled school at 4:30AM with radio announcing it at 5am.
Why you might be asking?
a) It was so students could do their homework.
b) In case the storm veered off into the sea. I was burned by this, a storm was coming I didn't study, oops storm moved out to sea and we got a dusting and had school.
c) If there was a few flurries at 4:30am they had school, then when it got worse when you got to school for class at 8am they then cancelled plus we didn't do a makeup.