Feelin' like a big hot mess? Here's where to chillax

It really is the humidity.

Thirty New York City residents died from heat-related deaths in 2011 (the last year for which numbers were available), according to the NYC Department of Health and Mental Hygiene.

At least some of those deaths were aggravated by the typically high humidity that afflicts NYC when the mercury soars. When both temps and humidity are high, the body can't cool itself down as effectively as it can in dry air, explained Dr. Tanveer Mir, director of outpatient palliative care at NYU Cancer Institute. High humidity makes it more likely you will sustain "heat injury," - which can range from lassitude and dehydration, to death.

First comes heat exhaustion (lethargy and dehydration). If you fail then to hydrate and cool down, you may get heat cramps (severe muscle cramps in the larger muscles of the body). A heat "attack," or heat stroke occurs when the body's core temperature reaches 104 or 105 and can occur in conjunction with dizziness and confusion. "Mild forms of heat exhaustion and heat cramps are reversible," but the liver, kidney, and brain damage, electrolyte imbalance and coagulating disorders caused in heat stroke may not be, said Mir. Once you're in heat stroke, "there is a 23 - 66% percent chance of death, depending on the availability of cooling mechanisms" to restore the body to normal temperature, she added.

"Prevention is so much better than cure," when it comes to avoiding thermal injury, said Mir. Do that by ditching your iced lattes ("caffeine is a diuretic and you wind up losing more water than you drink") for plain water or an electrolyte-crammed sports drink such as Gatorade. Dress in cool cottons (synthetics and silks don't allow the skin to breathe) and seek out the sanctuary of cool, air conditioned environments. Fans are no match for humid heat waves, so that means getting into a place with air conditioners and can dramatically lower the body temp.

Here are some unsweltering sanctuaries to check out: