That's a real tough one!
I often think about how nice it would be to live abroad where the sun shines 300 days a year and you could start each day with a swim in the sea. However, the thought of living without the British seasons makes it a lot less attractive, as we have something new happening every month of the year, so choosing the best one is very difficult.
That said, if I had to choose, it would have to be May
In this part of Cheshire it rains so much from October to April that May is usually a very welcome break from the almost daily soakings of the previous 6/7 months.
Then again, October is a great month, especially when the first morning frosts appear and the air at night is incredibly clear and fresh.
But now I think about it, you can't beat standing outside in the pitch black at 2 o'clock in the morning during December, when huge flakes of snow fall on your face and you hear the sound of snow crunching beneath your feet.
And then there's July - warm summer evenings when you can stay out in the garden until 11pm and the....
Oh I give up, I just don't know!