Your rabbit may well have a good amount of grass in its diet already but if it doesn\'t, make sure you introduce them slowly. A sudden change in diet can make itself all too apparent by giving your rabbit diarrhoea.
Make sure that you check your rabbit for cleanliness in the summer heat. Apart from the usual daily and weekly routines try to check their body from end to end every day for any unusual signs. Flies, especially greenbottles can be a very nasty parasite for rabbits. They lay their eggs and within a matter of hours they will hatch into larvae. Not too bad so far, but... after a few days they will start to feed on your rabbit by burrowing in and eating it. If your rabbit and housing are clean then your rabbit\'s natural grooming will go a long way to stopping this problem.
Check the rabbits water supply daily. Not only will your rabbits drink more but it will evaporate as well so extra vigilance is needed.
Shade. Position the shade so that the rabbits have an area of shade outside for midday lounging.