V4281051 wrote:a hat under your helmet which covers your neck and ears....
or just the hat would do, presumably?
I don't find sunscreen necessary in Britain - or a hat - but I needed both on tour in central Spain a few years ago. Of course I had to bring a helmet anyway, to put on in case I met a stroppy cop, but it was far too hot to wear as a sunshade and only made my headache worse!
I'd noticed farmers out in the fields wearing sort of trilby-like woven esparto hats, so I went in an ironmongers and bought one in my size (they had them to the nearest centimetre) for a couple of Euros. It was just the thing! I worried it might blow off downhill, but no, the leather headband shrunk slightly when sweaty and worked like a flap to keep it firmly wedged on at speeds up to 40mph (it helped to angle my head so the brim worked like a spoiler), whilst perspiration evaporated from the straw to keep my head cool.
I now see similar hats on sale in British garden centres for ten times the money, in one size doesn't fit all!
I still have my Spanish farmer's hat, and next time I go cycling somewhere that hot I'll take it along. Maybe I'll even bring it to the Birthday Rides!