Missouri City faces heat index values up to 109°F on Monday, Sept. 14, under a National Weather Service advisory in effect until 6 p.m. CDT.

The NWS Houston/Galveston office issued the advisory at 8:34 a.m. Monday, covering portions of south-central and southeast Texas. Fort Bend County and Missouri City are explicitly named in the alert zone. The agency warned that hot temperatures and high humidity may cause heat illnesses.

A second heat advisory is already scheduled for Tuesday, Sept. 15, running from 11 a.m. to 6 p.m., according to CW39 Houston. Actual high temperatures Tuesday are expected to top out around 95°F, above average for mid-September. The back-to-back advisories give Missouri City and Stafford residents two consecutive afternoons to plan around dangerous heat.

NWS safety guidance

The weather service urged residents to drink plenty of fluids, stay in air-conditioned spaces, avoid direct sun and check on relatives and neighbors. The advisory also recommended limiting strenuous outdoor activity to early morning or evening hours and wearing lightweight, loose-fitting clothing.

Outdoor workers should schedule frequent rest breaks in shaded or air-conditioned areas, the advisory said.

Heat stroke is a medical emergency. Call 911 immediately if someone shows symptoms.

More advisories possible this week

The heat may not break soon. Justin Ballard, the Houston Chronicle's newsroom meteorologist, wrote in the paper's Monday forecast: "Daily heat advisories are possible this week, so take breaks from the heat, drink plenty of water and be especially careful during the afternoon."

Forecast models suggest temperatures may ease toward the lower 90s around Sept. 22, though any meaningful pattern change remains uncertain, the Chronicle reported.

Isolated showers and storms are possible Tuesday but are expected to stay near the coastline, CW39 reported.