BROWNSVILLE, Texas (AP) - It's not yet summer but feels like it for millions of people in Texas as forecasters predict triple-digit temperatures in parts of the state.

The National Weather Service issued a heat advisory Wednesday for areas of South Texas, with highs expected to top 100 degrees and heat index values up to 115 degrees. NWS defines the heat index as a measure of how it feels when temperature and humidity are combined.

The advisory, warning of increased risk for heat exhaustion and heat stroke, covers the Rio Grande Valley and the Coastal Bend - including Brownsville, McAllen, Weslaco and Corpus Christi.

Forecasters also issued a heat advisory through 7 p.m. Wednesday for central and south-central Texas, covering Waco, Austin and San Antonio.

Summer begins Friday.

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