January - 2021 - not sure why I remember this month so fondly - a good blend of cold and mild - just felt brutal, as I want January to feel! - and snow in London. 2013/22 also good picks for this!
February - 2019 - easiest pick - a phenomenal month which was by far the best winter month ever! 2018/21 also good picks!
March - 2012 - the only saving grace of 2012 and therefore another easy option! 2017/20/22 also good picks!
April - 2011 - I preferred 2020 but that had to be used for the second of this exceptional April-may two hander that was 2020!
May - 2020 - Sublime. Unmatched. Doesn't get enough credit (a lot but still not enough). 21.1C max average at Heathrow - highest recorded for may and sunniest month ever. 2018 also close but too breezy from memory
June - 2017 - A lovely June which was remembered by the great solstice heatwave! 2018 was better - 2014/20/21 also on the same level
July - 2013 - Not the hottest July but the best in terms of UK wide summer - 2014/8 good. 2022 was not that amazing just very dry and obviously that great heatwave mid month but actually quite cloudy a lot of the time.
August - 2022 - a great August finally! Still think we can do better but in terms of the last decade was great - 2020 was also a v interesting month and as someone else said was a unique Bangkok feeling of hot unstable air!
September - 2016 - Not that good but I have to use this waste of a year somewhere. 2011/18/19/20/21 all were far better
October - 2018 - Strange in a way that I used 2018 here in the end but what an interesting month - especially rare to say about Autumn - great mix of warm, settled, unsettled, and cold at the end. I remember the 13-14th particularly for the 72 hour rainstorm. Great warm spell at the beginning and a lovely frosty sunny end. 2022 was also pretty good. 2020 also remember well but a sad sort of month
November - 2014 - literally nothing to say just remember halloween was warm but I guess that's in October anyway!!! 2021 was far better
December - 2015 - speaks for itself a very interesting month. Rarely like December anyway
This was more difficult than I thought it would be, I felt like I wanted to use 2018 for virtually every month and 2013-6 for nothing (they were were such boring years!) - I feel after the interesting run of years we've had from 2017-22 we are probably due some boring weather again now!