Another blast of Santa Ana winds Thursday prompted San Diego Gas & Electric to cut off electricity to thousands of residents in another of a wave of power outages that have continued off and on for two weeks.

A critical fire threat will continue across San Diego County as Santa Ana winds and dry conditions persist through early Friday, according to the National Weather Service.

The last time it was this dry in January, there were barely more than 500 people in San Diego. The year was 1850, and only a quarter-inch of rain had fallen in six months. It made the region ripe for wildfire — but that wasn’t much of a concern. The city’s population was clustered along the coast, far from the backcountry, where most fires burned.

An uptick in Santa Ana winds Wednesday afternoon through Thursday, combined with critically dry vegetation and low humidity, will result in elevated to locally critical fire weather conditions in County through late Thursday.

Scores of residents were urged to flee as fast-moving fires hurtled through bone-dry brush in Bonsall and Mission Valley Tuesday