My boys have been on reverse turn out since spring. In at lunch time for a three hour snooze, feed and haynet and then out again in the afternoon and overnight (unless it rains then they ask to come in). We've no shelter in their paddocks hence bringing them in for the hottest part of the day. However, for the past two days their stables have been horribly hot in the afternoon, and with no breeze either.
This morning I brought them in at 8, then put out again at 11 when the stables got too hot. They were shouting at the house to come back in, so I put them back in at half three when the stables had cooled, and will be in til about 7 now. How are your horses coping with the heat?
His field is quite sheltered. Out at night, in from about 7am until about 5pm. This is to avoid flies as much as anything although also because he's a pig and the grass is rich. His stable is quite large and airy. I tend to ride early morning then I sponge him off and leave him dripping - I don't sweat scrape so the cooling effect lasts longer.
When I've worked with horses and been around them full time I found that putting a cold, wet sponge behind their ears (pulse point) helped. Though some of them have quite strong opinions about whether or not you should do that! If you're out at work all day and not with your horse, of course you can't do that. Then it's the obvious - plenty of water available etc.
Mine are on the yard for dietary reasons (!) but have access to a big stone shelter and plenty of shade. Luckily where we are is quite breezy but they don't seem too fussed and spend as much time out in the sun as inside.