Fly balls have been leaving Major League ballparks in increasingly head-dizzying numbers in recent weeks, leaving pundits and fans alike to ask, "Are we seeing more homers than usual?"
As it turns out, the answer appears to be "Yes." In fact, we might be seeing something historic -- particularly here in the month of June.
According to the Elias Sports Bureau, players hit a combined 52 home runs Sunday, the most on any single day across baseball in more than a decade. That pushed the average number of home runs hit per game in June to 2.52, which would rank as the third-highest month in history in terms of home runs per game behind April 2000 (2.56) and May '00 (2.64).
When home run totals across baseball precipitously dropped from 4,934 in 2012 to a 20-year low 4,186 in '14, it was assumed that more stringent drug testing and other factors like increased pitcher's velocity, increased strikeout rates and increased use of bullpen specialists would prevent those totals from ever returning to their lofty peaks near the turn of the millennium.
In 2015, 4,909 home runs were hit in the Majors -- an 11 percent increase from the average of the two seasons prior. This year, the 30 Major League teams are well on their way toward combining for their first season of at least 5,000 total jacks since '09, signaling that power hitters are indeed making a comeback.
But 2016's home run bonanza goes beyond a simple return to prior peaks. Entering Monday's games, teams were hitting an average of 1.15 homers per game. If that rate were to remain the same through the end of the season, it would rank as the second-highest all-time behind only the 2000 MLB season, in which teams averaged 1.17 home runs a game. That suggests that something more historic is happening here than a simple course correction.
So why have so many home runs been hit this season? It's hard to pinpoint a singular answer at this point, but here are a few factors that have been contributing to 2016's long ball breakout:
More bang for the buck
Much has been made of the rising strikeout totals in baseball, and the numbers back that up. A new record for average strikeout per nine rate among Major League pitchers has been set in each of the past nine seasons, and 2016's 8.0 K/9 rate is on pace to rewrite the record books again.
Yet despite their rising strikeout totals, hitters are making the most of the times they do put the bat on the ball. According to Baseball Reference, the collective MLB home run per contact rate last September and October, where "contact" is defined as at-bats minus strikeouts, was 4.21 percent. That was the highest league-wide monthly HR/contact total in over six years -- until this year, as batters posted a 4.34 percent rate in May and an incredible 4.80 percent so far in June. Here's how that would rank among the highest monthly totals since 2000:
1. June 2016 (through 26 days) -- 4.80 percent
2. May 2000 -- 4.70 percent
3. March/April 2000 -- 4.59 percent
4. August 2004 -- 4.42 percent
5. May 2016 -- 4.34 percent
T6. Sept./Oct. 2015; August 2009 -- 4.21 percent
If that 4.80 HR/contact rate were to remain constant over June's final four days, it would be the highest monthly mark of this millennium, passing -- you guessed it -- May 2000 (4.7 percent).
Digging the long ball
A glance at the list of top home-run-hitting teams this year reveal some usual suspects, and some clubs one might not expect to see.
Last year's leader, the Blue Jays, aren't far behind in third place and the Rockies, who placed second in the 2015 National League home run standings, lead the NL with 102. But surprises can be found in the Rays, who currently rank fourth with 104 home runs after hitting a pedestrian 167 all of last season, and the Cardinals, who are just behind Colorado in the NL standings and sit just 36 homers shy of their '15 output.
Tampa Bay has not finished higher than the MLB team average in home runs since 2013, and the Cardinals have not done so since '11 -- the year of their last World Series championship. Each team's embrace of the long ball could be a indication of the game's increasing power trend.
Back in the swing of things
The Rays and Cardinals are not the only home run surprises in June. San Diego's Wil Myers is making his case for an All-Star Game selection after tying Jones for the Major League lead with 10 homers this month, nearly matching his career-high 13 jacks over his entire 2013 rookie season. Carlos Beltran has been on fire with seven homers in June, and he has already hit as many big flies this year (19) as he had during all of '15. Tampa Bay's Evan Longoria has secured the second nine-homer month of his career -- his first was way back in August '11. And Arizona's Jake Lamb has clubbed seven June home runs, which accounts for 70 percent of his career homer total before the '16 season.
Some of the names topping the home run charts this month -- players such as Jones, Edwin Encarnacion, Nelson Cruz and Davis -- would be expected. But the surprise players mentioned above have certainly helped push this June to historic status.
According to Elias, rookies have clubbed 78 homers in June, accounting for 8.73 percent of the total number of June homers in baseball entering Monday. Corey Seager is leading the charge with seven home runs this month, and at age 22 he leads the Dodgers in every Triple Crown category, including his 16 home runs.
The Royals' play-everywhere rookie Cheslor Cuthbert wasn't called up until May, but he has already slugged six home runs in June. Elsewhere in the American League Central, Indians rookie Tyler Naquin has clubbed six homers and become a major contributor to Cleveland's surge. And don't forget about the Rockies' Trevor Story (five home runs in June), who made homer history in his first week on a Major League field and is still tied for third in the NL with 19 round-trippers on the year.
We'll have to wait a few more days to see if June truly does rank among the best home run months in the history of professional baseball. But with the dog days of summer approaching, why limit the scope to just this month? We know that higher temperatures can cause pitchers to fatigue more quickly and lose grip on their pitches, giving hitters more opportunities over the heart of the plate. We also know that increased humidity lowers air density, allowing an easier path to the seats for fly balls.
In short, we may be just witnessing the beginning of a home run revival in baseball -- if not a wholescale transformation. For now, the best thing to do would be to bring your glove to the ballpark and get ready.
Matt Kelly is a reporter for MLB.com based in New York. Follow him on Twitter at @mattkellyMLB. This story was not subject to the approval of Major League Baseball or its clubs.