The cold weather is February. They can operate a lot more in November/December than they can in January/February. But they spready out the winter maintanance so won't open the whole park. But 15/20 years ago when they did Winter Weekends for hotel guests it used to be Forbidden Valley November/December and X Sector January/February. Then they tried to move to a more family based line-up for winter openings with very few big coasters open. Bad weather is what stopped the February half term openings though.