I have a feeling that your "tiger lilies" are, in all likelihood, orange daylilies. If the flowers were on a separate stalk from the leaves, they are daylilies. If completely brown, you can clear away the dead foliage and give them a good watering. They will likely revive and grow a new set of leaves. On the other hand, if they are true lilies, they will not make new growth until next year, if ever. Tiger lilies are subject to death by viral infection, particularly when under stress. By the way, true lilies have leaves that are attached to stems that are two to six feet tall. Daylilies have long strap leaves that arise from a crown, NOT from a tall stem.