A heat wave is gripping the Midwest and is shifting eastward, causing summer camps and outdoor activities to be canceled or delayed. On Monday, Communities have opened cooling centers and advised people to stay hydrated. The National Weather Service says the hot and humid weather is expected to last through most of the week. Some of the worst conditions are expected Thursday and Friday in the Ohio Valley, the Mid-Atlantic and Northeast. Temperatures are forecast in the 90s, with heat index values expected to exceed 100 degrees.