While I can't think of a way to change the download directory based upon the details of your request, what you could do, is to wait until the download is finished, then move the download to the directory you want.
Code:
on *:filercvd:{
  ;after a file has been received
  if (summer isin $filename) || (winter isin $v2) {
    ;check if summer or winter is in the file name
    .copy $filename c:\pic\ $+ $v1
    ;if it is, then copy the file to the appropriate directory
    .remove $filename
    ;then remove the file from the default download directory
  }
}

Comments added to explain the code.