Retail sales in May had their best month since January, as warmer weather and a stock market rally drew out shoppers who had spent March and April cooped up indoors.

Same-store sales across the board rose an estimated 3.9 percent, slightly beating expectations for a 3.7 percent boost, according to a measure from Thomson Reuters. In an attempt to tamp down volatility, the data only factors in revenue at locations that have been open at least a year.

The gauge outperformed April’s 2.2 percent upswing as well as the 0.5 percent increase from May 2012. Stripping out the effects of drug stores, last month’s retail sales were up 4.6 percent.

For much of the country, May was the first period of the year that truly felt like spring. Bitter temperatures earlier in the year had delayed seasonal spending on lighter clothes and home improvement products.

But consumers last month were also cheered by what analyst Ken Perkins called a “modestly better economic backdrop.”

The stock market initially surged. Home prices appear to be on an upswing. Consumer confidence reached pre-recession levels, according to the University of Michigan.

Some worrisome trends, however, kept retail sales from booming.

Gas prices increased last month in the first rise since February, frustrating many motorists at the start of the summer traveling season.

Private-sector job growth ticked up slightly in May, adding 135,000 positions but still falling far short of expectations, according to payroll processing firm ADP this week. On Thursday, however, the Labor Department said that first-time jobless claims dipped to 346,000 last week, a promising direction.

Still, consumers loosened their retail spending, said Perkins, who calculates a separate retail sales roundup via Retail Metrics Inc. By his count, sales increased 3.5 percent last month.

American Apparel led the pack with a 10 percent swell. Costco enjoyed a 5 percent upturn.

L Brands, however, slightly missed analyst predictions with a 3 percent expansion, compared to 6 percent growth a year earlier.