PHILADELPHIA (CBS) – Mother Nature is reminding us that summer isn’t over yet. A heat advisory has been issued for most of the Delaware Valley, including Philadelphia, for Monday and Tuesday.

They will be the hottest days this week.

Credit: CBS3

Check out the heat index values through Wednesday in the image listed below. The heat index is a measure of how hot it really feels when you factor in the humidity with the air temperature.

It will feel like we are in the triple digits on Monday and Tuesday.

This combination of heat and humidity can be very dangerous, especially for young kids, the elderly and people without air conditioning.

Here are some friendly reminders to stay safe during a heat wave:

1. Stay hydrated
2. Wear sunscreen and make sure you re-apply often
3. Wear light-colored clothing
4. Avoid strenuous activity
5. If working outside, take frequent breaks in the shade or indoors
6. Check on family, friends and the elderly
7. Bring pets inside
8. Don’t forget kids/pets in the backseat
9. Know the symptoms of heat-related illnesses (see image below)

Credit: CBS3

Take advantage of cooling centers, public pools and places that have air conditioning.

Stay safe and think cool – winter begins in 125 days.

CBS3 Meteorologist Tiffany Savona contributed to this report.