The US southwest baked under an unrelenting heatwave for a fifth day on Friday, putting power systems to the test as more records were expected to be broken before a moderating trend sets in next week.

The National Weather Service issued excessive heat warnings for five states — California, Nevada, Utah, Arizona and part of Colorado — where the heat has been extreme even for a region where temperatures often exceed 100 degrees Fahrenheit (38 degrees Celsius).

“Every year it’s hot in the southwest,” said meteorologist Bob Oravec of the National Weather Service Weather Prediction Center in College Park, Maryland. “It just seems to be more newsworthy when you have temperatures of 115 or so day after day. It’s pretty hot.”

The heatwave stressed power systems in Texas and California this week, but they withstood the record demand.

Power grid operators in both states, however, continued to urge consumer to conserve energy to reduce strain on the electric system and avoid outages as homes and businesses kept air conditioners cranked up.

In Texas, where temperatures have moderated, demand hit a record on Monday, according to the Electric Reliability Council of Texas (ERCOT), which operates the grid in most of the state.

California’s power demand peaked on Thursday at 41,364 megawatts and was expected to come in close to that level on Friday, according to the California ISO, which operates the grid in most of that state. One megawatt can power about 200 homes on a hot summer day.

Among the cities where record highs were expected to be set were Phoenix at 117 degrees (47 degrees Celsius) and Sacramento, California, at 108 (42 degrees Celsius), the weather service said. Many others were expected to come close to tying or breaking their daily records.