<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/south-tx-highs-7jun19.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/south-tx-highs-7jun19.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/south-tx-highs-7jun19.jpg?v=ap&w=980&h=551 800w" > Actual high temperatures in South Texas on Friday, June 7, 2019.

At a Glance South Texas is typically hot in June.

However, a heat wave topped one all-time June heat record.

Unofficial heat indices rose to 128 degrees Friday in Brownsville. South Texas is searing in an oppressive heat wave that is sending temperatures into the triple digits, already topping one all-time June record and pushing heat indices above 120 degrees in some locations.

Brownsville, Texas – in the lower Rio Grande Valley along the border with Mexico, just west of South Padre Island – soared to 104 degrees, its hottest June high temperature in records dating to 1878, topping the previous June record of 103 degrees on June 26, 2012, and June 19, 1918.

It was only 2 degrees shy of the city's all-time record high, 106 degrees, set on March 27, 1984.

(INTERACTIVE: Current South Texas Temperatures)

A breeze from the Gulf of Mexico only made the heat worse. It wasn't a dry heat.

The combination of stifling heat and dew points near 80 degrees produced unofficial heat indices up to 128 degrees Friday, the National Weather Service in Brownsville tweeted.

This dangerous combination of heat and oppressive humidity prompted the NWS to issue excessive heat warnings from Corpus Christi to the lower Rio Grande Valley , an area typically used to triple-digit heat.

The heat indices above 120 degrees even busted above the color table on a map the NWS tweeted Friday.

(MORE: What is the Heat Index and Why is it Used? )

A reporting station at Falcon Lake, a reservoir along the Rio Grande River between Laredo and McAllen, recorded a high of 116 degrees Friday, the nation's hottest temperature and only 4 degrees shy of the all-time state record high of 120 degrees set during the Dust Bowl at Seymour on Aug. 12, 1936.

South Texas often holds the title of the nation's hottest temperature in the colder months of the year, while most of the nation shivers. By June, it typically cedes that title to Death Valley, California.

In this case, however, Falcon Lake (116 degrees) was 9 degrees hotter than Death Valley Friday and equaled Death Valley's hottest temperature so far this season.

Daily record highs were also tied or set Friday in Laredo (109 degrees), McAllen (106 degrees), Harlingen (104 degrees) and Corpus Christi (102 degrees).

The searing heat indices continued into Saturday and Sunday as well.

The heat wave was expected to last through the weekend, then ease off to more typical lower to mid-90s highs by Tuesday.

(MAPS: 10-Day U.S. Forecast Highs and Lows )

So much heat and humidity built up that thunderstorms eventually erupted that could be seen 60 miles away in Corpus Christi.

According to weather historian Christopher Burt's "Extreme Weather," Corpus Christi is the nation's hottest major city by heat index, averaging a 110-degree peak daily heat index from July through August.

(MORE: 6 Things You Should Know About Heat Waves)

Burt said heat indices during the record mid-July 1995 heat wave reached 126 degrees in Waterloo, Iowa, and 129 degrees in Philadelphia.

There are no world records kept for extreme heat indices, but Burt says the world's worst combination of heat and humidity is likely along the Persian Gulf, Ethiopia's Red Sea coast and Somalia's Gulf of Aden coast, where summer heat indices can regularly soar to 135 to 145 degrees.

In July 2015, a heat index of 164 degrees was measured at Bandar Mahshahr, Iran , along the Persian Gulf coast.

The highest known heat index measured in the world, according to Burt, was 178 degrees, from a temperature of 108 degrees combined with a phenomenal dew point of 95 degrees in Dhahran, Saudi Arabia, on July 8, 2003.