Ok, this has happened a couple of times now and is not pleasant at all.
Basically, when it's hot like this and if I'm not careful, I become quite poorly when out on the bike. Last year we were on a ride around Ladybower, the temperture was around 26 degrees, and after a couple of climbs I started to get a terrible headache. It was so bad that it felt like my brain was banging around inside my head. Half an hour later I started vomiting (water), and had to abandon the ride.
Last night I started to get similar symptoms but managed to get home before it got too bad. Nevertheless, I had to go to bed in order to clear the headache.
I'm quite conscious of how much water I drink and try to stay well hydrated. In the Ladybower example, despite being sick the only thing coming up was water. I really fancy doing some sort of biking holiday abroad but worried about suffering in the heat.
Anyone ever experience something similar?