The Met Office does, and have done for years. The definitions used to be in degrees Fahrenheit, but are now in Celsius. They used to publish them on their website but for some reason they removed them many years back.
In summer (May to September), the definitions are:
Very hot: 8C or more above average
Hot: 6C or 7C above
Very warm: 4C or 5C above
Warm: 2C or 3C above
Average 1C below, average or 1C above
Rather cool: 2C or 3C below
Cool: 4C or 5C below
Very cool: 6C or more below
These are in reference to the latest 30-year period, so locally to me 26C in mid-June would have been hot in 61-90, but it's only very warm these days.
Note that cool (as opposed to rather cool) would mean highs of 17C in London, or 16C in Kent, 14C in Rochdale and 13C in Edinburgh in mid-June. You can add a degree to those figures for the end of June/start of July.
Originally Posted by: Retron