We’ve reached a transitional period of the Major League Baseball season. It’s two months after Opening Day, and there’s now enough sample size that you can start to trust that what you’ve seen from teams or players so far isn’t just a fluke.
We’re also not yet to the dog days of summer, when the long season becomes a drudgery, with contenders resting key players with an eye toward October and pretenders just playing out the string listlessly.
What does that mean for baseball gamblers? It means we have to decide whether the June Swoon is a real thing, and if it is, how do we prepare for it when trying to pick games?
What is the June Swoon?
Like many of baseball’s unwritten rules, it’s tough to put a finger on exactly what is meant by a June Swoon. Essentially, it means a team was doing well, and then began losing games.
What is special about June that causes winning teams to fall apart? It could be that the wear and tear of two months has caused injuries to crop up, maybe nothing that will sideline a player—just something that will nag and keep him from playing his best. Think the Angels’ Mike Trout, who put up a career-worst 0-for-26 (and counting) slump this month.
It could be clubhouse conflict, as little annoyances begin to blow up after a group of players has been together since March.
Or it could just be that “June” and “swoon” rhyme, so we have a catchy name for the cold spells and losing streaks that happen to every team at some point—usually multiple points—during the marathon season.
Baseball is a zero-sum game. Every June loss must, by definition, also produce a June winner, but we don’t hear talk of June hot streaks the same way we do the swoon. For some reason, “June boon” just hasn’t caught on.
But a quick internet search shows that just about every team, from the Twins to the Rockies to the Cardinals to the Yankees, think that they suffer from the June swoon, if not every year that most of them.
Is There a Swoon?
We looked at the last three full seasons—2018, 2019 and 2021, not counting the 60-game 2020 pandemic season—to try to find evidence of the June Swoon.
We looked at the six teams that were leading their respective divisions at the end of play on May 31, just prior to any swoon would begin. Then we looked at those same teams at the end of play on June 30.
So what did the results show? Are they useful for gambling? Is there a June Swoon?
Well … kind of.
The 18 division leaders over those three full seasons had a .611 combined winning percentage through May 31 and an average lead of 3.1 games over the second-place team in their division.
In June, they had a winning percentage of .536, which is 75 points lower than they had in the first two months.
The average division lead was cut in half in June, to 1.5 games. Six of the 18 teams in first place on May 31 lost the division lead in June. Seven division leaders played below .500 in June.
The 2021 Rays are a good example. They were 35-20, .636, on May 31, leading the AL East by two games. On June 30, they were three games back in the East, after going 12-14, .462, in June.
Is It Fatal?
The June numbers look pretty bleak. So why did we say that the answer to “Is there a June Swoon” was “kind of”? Because for most of the teams that swooned in June, they were back reaching for the sky in July.
Those same 18 teams combined to post a .569 winning percentage from July 1 through the end of the season, jumping 33 points higher than their June mark. Their average division lead at the end of the season was 1.1 games.
So, for the most part, a June swooner can be expected to bounce back immediately afterward, meaning that the fabled swoon may just be the “before” in a lesson on regression to the mean.
Going back to the example of the 2021 Rays—after going .462 in June, the Rays then went 53-33 the rest of the way, posting a .654 winning percentage that was even better than their percentage at the end of May. They regained the division lead and won by eight games.
That’s not to say every team bounces back. The 2021 Mets were .574 through May, .500 in June, and .412 the rest of the way. The 2019 Phillies and Cubs and 2018 Nationals also continued to lose after their June swoons. But of the 15 teams that saw their winning percentages drop in June, 10 saw them increase again in July and beyond.
Teams are going to slump at times during the year, and if a team is in first place at the start of June, it could be that they haven’t had their slump yet. But the June Swoon is no different than a cold stretch any other time during the year. For MLB betting purposes, expect the best teams to slow down a bit in June, then bounce back big the rest of the way.