Rainburn

It started with neck and upper body sores that looked a bit like rainburn - but usually they had only two or three of them.

I have seen sunburn/windburn and 'rainburn' affect horses over the years but this did not fit any of those causes […]

He peered out, glancing at the sky. 'We'd better get under cover before it starts raining,' he said, breathing heavily. 'We don't want to get rainburn.'