Thursday's heat index to push 120-degree mark

HARLINGEN, Texas (ValleyCentral) — A strong subsidence pattern, where large‑scale sinking air warms as it compresses, is driving temperatures sharply upward across the Valley. This setup produces extremely hot conditions, with heat index values climbing even higher.  Forecast highs for tomorrow are expected to reach the upper 90s to low 100s, but the combination of heat and humidity [...]