Humidity at PG&E Substation Likely Cause of Massive December San Francisco Blackout ^73.4%

KQED - By Katie DeBenedetti - 5/9/2026, 12:19 AM

Negativity Bias 17.8% - Post Hoc (False Cause) 12.1% - Availability Heuristic 10.4%

The fire at a PG&E substation that sparked a major outage in December, cutting power for about a third of city residents during the holiday weekend, was likely caused by a buildup of humidity, among other factors, according to an independent report released Friday. The 70-page analysis by engineering consulting firm Exponent found that... more