New Jersey’s first heat wave of August is expected to arrive on Tuesday and could last through Friday as a tropical air mass settles over our region and pumps in hot, humid air. Heat and humidity will become increasingly more oppressive as the week progresses. An Excessive Heat Warning and Heat Advisories are now in effect for Wednesday and Thursday, when dangerously high Heat Index values of 100-105° or greater are expected. If you must be outdoors during the afternoon or early evening hours, wear light clothing, take frequent breaks, and drink plenty of water. Check on your friends, family, and neighbors who may be susceptible to heat illnesses, especially if they do not have air conditioning. National Weather Forecast.