Texas’ electricity regulator warned residents and businesses to reduce the amount of powerthey use on Monday as the heat index was forecast to soar above 100 degrees Fahrenheit, putting a strain on the state’s grid and potentially leading to rolling blackouts across the state.

Thermostats should be turned up at least one degree Fahrenheit, and major appliances should not be used from 2 p.m. to 8 p.m. Central time on Monday, according to an alert from the regulator, the Electric Reliability Council of Texas, which manages about 90 percent of the state’s electric load.

ERCOT does not expect systemwide outages. The alert is one step before an Energy Emergency Level 1, which would allow the regulator to tap electricity from other grids nearby when reserves are dangerously low. If the situation worsens, ERCOT can order transmission companies to cut off power to industrial customers and residential consumers.