BROWNSVILLE, Texas (CBSDFW/AP) — It’s not yet summer, but it sure feels like it is for millions of people in South Texas, where triple-digit temperatures are forecast.

The National Weather Service has issued a heat advisory for the Rio Grande Valley and the Coastal Bend warning that temperatures could top 100 degrees Wednesday with a heat index of up to 115 degrees. The Coastal Bend includes Brownsville, McAllen, Weslaco and Corpus Christi.

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The heat index represents how hot a person is likely to feel outside given the temperature and humidity.

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Forecasters also issued a heat advisory for central and south-central Texas, covering Waco, Austin and San Antonio.

The advisories warn of an increased risk of heat exhaustion and heat stroke in the affected areas.

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Summer officially begins Friday.

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