The first stretch of 100s is hitting the Sacramento and San Joaquin Valleys. These temperatures can quickly lead to heat-related illnesses like heat exhaustion or even more serious -- heat stroke.

Signs of Heat Stroke

An excessive heat warning is in effect until Wednesday morning with highs in the lower 100s through at least Tuesday. Overnight lows will not bring much relief, only cooling to about 70 degrees. This means we’ll have to work harder to stay cool for a longer period of time.

Staying hydrated, limiting time outdoors and staying in air conditioning can help relieve some of the stress heat can put on our bodies. If you have to be outside, wear light clothing to stay as cool as possible.

Also, look before you lock. Heat will build quickly in the car and can lead to deadly conditions inside.

Heat can be especially tough for the elderly, so it's best to check in to make sure they are handling the heat okay.

The San Francisco Bay Area is also suffering through this heat with temperatures in the 90s.

The Bay Area will start to see cooler weather Tuesday. The valley will take a little longer to feel relief. Highs will stay close to 100 degrees through Wednesday and then drop to widespread 90s by Thursday.

WATCH ALSO:The heat costs money. Here are tips to save this summer | Daily Blend