There are no Mondays in February.
Well, the Mondays do exist. They still come between Sunday and Tuesday. But they aren't school days.
In the district I sub for (and probably others as well) the end of the semester occurs on the Friday of the week that contains January 31st. The district gives its teachers a planning day on the Monday following the end of the semester. Non-student day means that there is no need for subs. This falls on the first Monday in February.
The second Monday in February is Lincoln's Birthday. I've noticed that it has become less of a holiday in recent years. I wonder why. Well, it doesn't really matter. The district I sub for still takes it off, and that makes two three-day weekends in February.
Now, the third Monday in February is still widely celebrated: President's Day (or formerly Washington's Birthday). That makes three three-day weekends in a row.
And as for the fourth Monday in February...well...um...okay, it's not a holiday. It's a school day. So, technically, there is one Monday in February. But it happens at the end of the month. And saying "there's only one Monday in February" doesn't quite have the same ring to it.