While temperatures swelled and the coronavirus outbreak continued to ravage the world, Costco Wholesale (NASDAQ:COST) rolled merrily along. After market close on Wednesday, the retailer unveiled its August sales metrics, nearly all of which grew at double-digit rates compared to the same month of 2019.

All told, the company recorded a 13.2% increase in sales across all of its stores to just under $13.6 billion, due in no small degree to online sales that more than doubled (rising nearly 102%, to be exact). Costco's U.S. outlets -- the core of its operations, as they comprise 69% of the global total -- collectively grew their take by 12.5%.

Those figures don't account for changes in gasoline prices and foreign currency movements. With those factors included, Costco's adjusted total global sales rose at a 14.5% clip.

Female shopper in a face mask picking an item from a store shelf.

Image source: Getty Images.

Zooming out to annual figures for the 52-week period ended Aug. 30, sales rose by 7.7% companywide on a non-adjusted basis. The rate adjusted for changes in gasoline prices and foreign exchange was 9.2%.

Costco typically does not offer commentary when releasing its monthly metrics. However, judging by those monthly figures and recent company dynamics, it appears that the retailer continues to benefit from its position as a reliable, go-to supplier of many types of goods during the pandemic. What helps is its wide variety of products, making a Costco warehouse a one-stop shop for people still wary of venturing out too much.

Investors don't seem too surprised by the August performance, judging by how the stock was trading in mid-afternoon action on Thursday. It was down by 2.8%, only slightly bettering the 3.6% dip of the S&P 500 index.