Each year during the summer, radio habits change and certain formats see a seasonal increase in audience that’s unique to the warm weather months. And each year, Nielsen tracks these developments by naming the format that grows its audience the most the format of the summer.

Here are the winners from the past five years by percent of increase in overall audience share (persons 6+).

And with the summer of 2017 upon us—and the release of Nielsen’s May portable people meter (PPM) ratings—it’s useful to read a bit of the tea leaves in the data trends as we look ahead to the season. To do so, we’ll review listening trends for a handful of radio formats (including former summer winners) from the most recent three months for insight into what may happen this summer.

Overall, we can see Classic Rock—last summer’s outstanding format—surging and already outpacing last year’s numbers. A year ago in May 2016, the Classic Rock format had a 5.1% share of the listening audience (persons 6+). At the same time, Urban Contemporary is quietly setting some new benchmarks, tying the all-time mark this month in total listener share.

When we dive into the results among Millennial listeners (18-34 year-olds), Urban Contemporary jumps to the top of this small analysis, and again sets a new record this month with a 7.0% share, up from 6.5% in May 2016. Country is also growing its Millennial audience, which increased from 7.2% in the Holiday book to 8.7% in May.

And finally on a 25-to-54 audience basis, Country remains at the top of this summer horserace pack, moving up one-10th of a share-point in each of the past few months. Classic Rock is also moving steadily upward, while Classic Hits has been up and then down. We also see that Urban Contemporary set another new record in May among 25-54 year-olds.

Over the next three summer ratings books (June through August), we’ll be keeping a close eye on these formats, particularly Urban Contemporary, which is already having one of its best years in terms of PPM data. Classic Hits and Classic Rock have attracted solid listener bases in each of the past three summers, but only time will tell if American radio listeners will sing a different song this year.

Data used in this article is inclusive of multicultural audiences. Hispanic consumer audiences are composed of both English and Spanish-speaking representative populations.