1709? There should be reasonably reliable records from the Middle East, India, China, and the Americas, both north and south. A broader picture would be interesting.
Well known for a long time. From a 1969 book:
“This year was perhaps the most terrible that France had ever known. On 12 January, the cold came down. In four days the Seine, all the rivers and the sea on the Atlantic coast were frozen solid. The frost lasted for two months; then there was a complete thaw; as soon as the snow which had hitherto afforded some protection to the land, melted away, the frost came again, as hard as ever. The winter wheat of course was killed as were the fruit, olive and walnut trees; and nearly all the vines; the rabbits froze in their burrows; the beasts of the field died like flies.” (Mitford, Nancy, 1969. “The Sun King: Louis XIV at Versailles”, Sphere Books London 256 p.)
From a 2004 scientific report:
Probably the coldest winter across Europe (as a whole) in a series starting 1500; combining proxy & instrumental data. [University of Berne / RMetS / ‘Weather’ 2004) ]
One thing I noticed was the Brits were unable to take Lower Canada in 1710 ~ jus' couldn't do it.
Probably darned cold!