Here are some suggestions. Feel free to add some more.
* stake any large stems; tie the stem very well to the stakes; allow the stakes to go deep into the soil or otherwise they will go airbone.
* paniculatas tend to be more brittle than other varieties so consider hard pruning before the storm if winds will be very high in your area
* If winds will not be very bad but still high, consider doing without blooms for the rest of the season. Blooms absorb water and become heavy so deadhead them by cutting the strand that connects the stem to the bloom (do not cut the end of the stems as this is where Spring 2013 blooms arise from in some hydrangeas). Paniculatas and oakleafs produce the largest blooms so these types of blooms would worry me more than those of a macrophylla.
Paniculatas bloom on new wood so their blooms can be pruned and displayed indoors. Oakleafs and macrophyllas bloom on old wood (reblooming macs also bloom on new wood)
* If you deadhead blooms or prune stems, consider displaying them indoors. When they get old, use them as mulch if the blooms have no fungal issues.
* Someone suggested tieing all the stems together too but I have not tried this idea. It sounds like it would help control stems battered by gusts but only up to a point.
* If the winds are going to be somewhat bad, consider: Cover with upside-down plastic garbage bags. Hold with bricks. Drill some holes in the bags. You can also use upside down garbage cans or boxes. But if you expect to be hit with a lot of winds then these actions may be for naught; better to prune them stems down.
* If you get salt water, there may be parts of the plant that die. Water more often than normal to try and dilute the salt away.
* Do not fertilize; leave that for 2013. If there is leaf damage, wait for the plant to either go dormant or wait for the plant to leaf out. The new growth may die off after a freeze or during the winter but the plant roots should not if all else if ok.
* Mulch and compost absorb a lot of water. Use them around the shrubs if you expect pools of water to form. Then move them elsewhere to dry out if saturated with water.
* Expanded shale can also absorb water. Oakleaf hydrangeas are very sensitive to wet feet so check how their soil is after a storm.
* Consider laying down potted hydrangeas if you cannot move them into a garage or similar protected location.
Good luck, Luis
PS - Most of the damage to landscape from hurricanes should be from tree damage so address tree problems first and then check the hydrangeas. Watch out for downed power lines.
Luis, excellent advice, not only for hydrangeas but for other flowering shrubs. Thank you! 
In the southern areas of the forecast storm area, these protective approaches might also be helpful for roses, so I'm going to put a link under Roses.
If I'd had advice like this in early December 1995, I might not have lost as much of my individual rose bushes as I did in the mighty storm of December 12, 1995, wherein over a million people in northern California lost power due to hurricane-strength (approx. 85 mph) winds.
Cynthia H.
Sunset Zone 17, USDA Zone 9
In the southern areas of the forecast storm area, these protective approaches might also be helpful for roses, so I'm going to put a link under Roses.If I'd had advice like this in early December 1995, I might not have lost as much of my individual rose bushes as I did in the mighty storm of December 12, 1995, wherein over a million people in northern California lost power due to hurricane-strength (approx. 85 mph) winds.
Cynthia H.
Sunset Zone 17, USDA Zone 9