Remove any mulch under your hedge,
especially any type of weed barrier or plastic sheeting. Rake away any leaves, twigs and debris that may have accumulated under the hedge. Bare ground will dry out your hedge much faster.
Scrape the stem of the hedge trees with spade. Strip as much bark off of the stem as you can. Cutting open the bark of the hedge will help to dry it out much faster.
Dig a one-foot-deep trench looping around your hedge. At one end of the trench dig a drainage channel to carry water out of the trench. The trench will expose roots that will help to wilt the hedge. The trench will also help to dry the soil out around the hedge and drain water away from the plants.