Quick Answer:  Yes they can get laminitis at any time of year, spring grass is a big one and we are all mostly aware of those dangers, but we might be thinking that our horse is safe at other times.  Not so, they can get it at any time.

Spring grass contains a lot of sugar to fuel its new growth and so if our horses eat too much of it, so that it overwhelms their insulin response, then laminitis is a big possibility.

At other times of year, don't be fooled though, too much sugar is always going to be a risk and they can get this from our over fertillises, lush grassland.  Horses do eat for many hours a day but they are disigned to walk constantly while searching for enough grass. Our horses often can move a few yards and get enough grass without any more effort.

There are other causes of laminitis too, in winter solid hard ground causes concussion, sometimes enough to cause a problem.  So each season has its risks and as we love our beasties very much, we need to be vigilant, especially if they are getting fat.