"February is not a month of the summer."
Translation:Febrero no es un mes del verano.
I found this reference
All of the names for months are masculine: el enero, el febrero, etc. It usually isn't necessary to use the el except when giving specific dates.Note also that the names of the month are not capitalized in Spanish.
Now I'm thinking when would we possibly use it. I thought maybe when its an object but I doubt that happens. So leave it out and you reduce the risk of being wrong.