The maximum daily temperature north of the border was 15.3C for the month – 2.4C above the May average.
Aberdeenshire and Banffshire recorded even higher temperatures, with the gauge 3C above the daily average for the month.
Scotland’s monthly rainfall was also well down for May.
Just 46.1mm fell across the country – only 55 per cent of what Scotland would normally get for the month.
The last time Scotland had a warmer May was in 1910 – four years before the start of the First World War – when Met Office figures were first recorded.
Sunshine hours were well up at 229.7 for the month.
The amount was almost 30 per cent higher than Scotland’s average sunshine hours for the month.
A total of 245.3 hours of sunshine were measured across the UK last month, according to the Met Office.
This is more than any May since existing records started in 1929.
It was also the warmest May for Britain on record.
The average daytime maximum temperature was 17C, just beating the previous all-time high of 16.9C set in May 1992.
Met Office data for temperatures go back to 1910.
Despite thunderstorms bringing showers and flash floods to parts of the country at the end of the month, rainfall across the UK in May was less than two thirds (64 per cent) of the level expected.
Rainfall in Scotland was just 55 per cent
England was 72 per cent of the long-term average for the month, while in Wales it was 62 per cent.
Northern Ireland’s rainfall was 80 per cent of the average.
Tim Legg, from the Met Office National Climate Information Centre, said: “Increased sunshine during the month has helped to keep daytime temperatures high, leading to it provisionally being the warmest May since records began in 1910.
“It is also likely to be the sunniest May since 1929 too.”
Derbyshire and the Isle of Wight all recorded daytime maximum temperatures 3C or more above their long-term average temperatures for May.