The beauty of turf is that it can be laid at any time of the year! However, there are one or two things to bear in mind. Whenever you lay turf, make sure that it stays damp until it has rooted into the soil below. This means that, during the summer, you will have to put extra care into watering your turf. Turf laid during the winter is not at such risk of drying out, but root growth is slower, and you may have to wait a little longer before you can use your new lawn.
(I wrote that all myself...... honest!)