I always reckon on 7 to 8 deg C for an average of 3 days, night and
day temperatures, stops the grass from growing. Likewise but in
reverse to start growing and needing a cut.

Which therefore means I will be cutting my grass on Xmas day probably
this year.

I always get asked this, on my rounds. It used to be end of October no
more regular cutting, but its now well into Nov. Similarly I start
cutting regularly mid March as opposed to end of March.