It isn't output that gets knocked down by the weather. It's signal strength (and corruption of the incoming signal) at your antenna.

Leaving aside the problems of reflected signals, your first line of defence is an F-ing great Yagi as Foulestroupe says.

However, there is a loop of gain directly behind a Yagi - just like a unidirectional microphone. This can be reduced by a second reflector behind the main one. Book on aerial technology will help (ham radio ones are good). If your next door neighbour is a CB enthusiast running huge boots and leaving his swr meter in circuit, you will need to talk to him. If I wanted to be nasty I could wipe out TV for about 100 yards, but I was running a 1kw Bremi burner up a 5/8wave Starduster - audible from Kent to Wales. I don't do it any more of course.

Next step - masthead amplifier. Next best - loft amplifier - not much use - room amplifier. The further the amplifier is from the masthead the more shit there is in the signal it amplifies.

There is some difference in digiboxes. Some have better discrimination. Generally I have found the old ondigital ones that used discrete components best.