def month_to_season(monthnum):
    """
    Converts month numerical value to season numerical value.
    0 - Winter
    1 - Spring
    2 - Summer
    3 - Fall
    """
    if (0 <= monthnum <= 1) or (monthnum == 11):
        return 0
    elif 2 <= monthnum <= 4:
        return 1
    elif 5 <= monthnum <= 7:
        return 2
    elif 8 <= monthnum <= 10:
        return 3