It seems odd to me that an organization would try to fund raise around the same time that lots of people have increased fuel bills from heating, and expensive festivals like Thanks Giving and Christmas to pay for. No doubt there's some reasoning behind it but I'd definitely have thought that fund raising at almost any other time would be more successful.
Christmas, and by extension the holiday season, has a longstanding tradition of charitable giving (probably originating around Christianity?). People are just in a giving mood around the end of the year. It's not unusual for 30% of all donations to occur in the last month of the year. So it's by far the best months for fundraising.