An excessive heat alert has been issued by the The National Weather Service, with the alert officially taking effect Thursday afternoon and lasting until Friday afternoon.

The alert extends from northern Connecticut and Rhode Island to southern New Hampshire and includes all of Massachusetts except for parts of the Berkshires, Cape Cod and the Islands.

Temperatures are expected to reach between 95 and 100 degrees during the alert, with the heat index, making it feel as though the temperature is actually 105 degrees. Temperatures will be particularly intense from noon to 8 p.m.

The National Weather Service is advising that the heat can cause illness if not taken into account, and that children, sick and the elderly should refrain from strenuous physical activities and everyone should do the following.

• Wear lightweight and loose fitting clothing whenever possible
• Drink plenty of water and fluids.
• Avoid prolonged exposure in the sun
• Try to stay in an air-conditioned environment
• Regularly check up on relatives and neighbors that are young, old or sick.

The Occupational Health and Safety Health Administration also recommends scheduling frequent rest breaks at work in shaded or air-conditioned environments if possible.