Costco stock jumps after December sales climb — what matters before Friday’s openNEW YORK
Jan 9, 2026, 05:17 EST — Premarket Costco Wholesale Corp’s (COST.O) shares rose 3.7% on Thursday to $915.31 after the warehouse retailer reported December sales results. Yahoo Finance The monthly report matters because it lands between earnings and can quickly reset expectations for traffic, pricing and renewal-driven demand. Costco’s numbers are also watched as a bellwether for big-box retailers including…