There are relatively few health issues specific to New York. In coastal regions, swimmers and boaters should be respectful of the ocean's powerful surf. Adhere to posted riptide warnings, and to be safe stick to areas that have lifeguards. Summers can be hot and humid throughout New York, especially at lower altitudes and in the southern part of the state; wear light-color clothing in summer, drink plenty of fluids (and bring along bottled water on hikes, boat trips, and bike rides), and consider staying indoors during the hottest times of the day.
Mosquitoes, seasonal black flies, and just about every other annoying insect known to North America proliferates in New York. Exercise common precautions and wear appropriate lotions or sprays.
Lyme disease, which is spread by bites from tiny deer ticks, is not uncommon in New York, especially where there are significant deer populations (eastern Long Island, the Hudson Valley, and most rural areas). Symptoms vary; most victims show a red ring-shape rash around the deer-tick bite, somewhat resembling a bull's-eye and appearing from one to several weeks after the incident. Flulike symptoms (fever, achy joints, swelling) often follow. One common problem is delayed diagnosis; the longer you go without treatment, the more severe the disease's effects.
When spending time in areas where ticks are a concern, wear long-sleeve clothing and pants, tuck your pants legs into your boots and/or socks, apply insect repellent generously, and check yourself carefully for signs of ticks or bites. It's a good idea to don light-color clothing, as you'll have an easier time sighting ticks, which are dark. Remember that the more common wood ticks do not carry the disease, and that deer ticks are extremely small—about the size of a pinhead.