Costco Wholesale (COST 0.13%) continues to post encouraging fundamentals, as consumers become more encouraged to abandon coronavirus pandemic stay-in-place measures.

On Thursday, the retailer released its latest set of monthly sales figures. These revealed that companywide net sales were nearly $15.6 billion in May, a robust 24% higher than in the same month last year. This was on the back of comparable sales that advanced by almost 23%. Online sales, meanwhile, rose at a 12% clip.

Costco did note that May 2021 contained one extra shopping day compared to May of last year; it said this affected sales by roughly 2 to 2.5 percentage points.

Woman and small girl shopping for groceries while wearing face masks.

Image source: Getty Images.

Loosened coronavirus restrictions and steep declines in COVID-19 case numbers, as is the trend in the company's core market of the U.S. just now, don't tell the whole story. Costco was a default shopping destination even in the thick of the pandemic, as customers considered its stores a reliable source of staple items like toilet paper and sanitizing products.

As a result, and in contrast to a great many retailers who had to contend with mandatory shutdowns, Costco managed to grow its business. In the company's fiscal 2020, which ended last Aug. 30, its net sales rose by 9%. Looking at the first quarter of fiscal 2021 -- occurring as it did at the start of a fresh surge in coronavirus cases -- net sales growth was even higher, at 17%.

At the end of May, Costco operated 809 warehouses. Of these, 559 are located in the U.S. and Puerto Rico, 105 are in Canada, and Mexico is home to 39. The remainder are scattered throughout Europe and Asia.

Investors have been bullish on Costco for weeks, and Thursday was no exception. The company's stock rose by almost 0.9%, while the S&P 500 slipped by 0.4%.