"Is the month of March in the winter?"
(No, it is in Spring!)
Since "el invierno" is winter, your choice of months could include "diciembre", "enero", "febrero" and part of "marzo" depending on how many letters it is.
It means "in what season is the month". Probably better to use "ser" here. "en que estación es el mes?"
Marzo means March in Spanish.
The 10th of March in Spanish is "el diez de marzo."
You can say "Mi cumpleaños es el treinta de marzo".
In Spanish, March 24th would be "el veinticuatro de marzo"
El Mes = The Month
January
'El invierno' is 'Winter'.
el invierno
"El invierno" is "winter" in English.
summer.