Even for the best sluggers in baseball, reaching 10 homers in one calendar month is a notable achievement. But 15 or more? It doesn’t happen often. 20? Only one man in MLB history has done that: Sammy Sosa in June 1998.

These are the Major League records for the most single-season home runs hit in each of the months that typically make up MLB's regular season, with March/April and September/October (postseason not included) grouped together.

March/April: 14 HR
Albert Pujols (2006 Cardinals), Alex Rodriguez (2007 Yankees), Cody Bellinger (2019 Dodgers), Christian Yelich (2019 Brewers)

Cody Bellinger and Christian Yelich, who would go on to finish first and second, respectively, in the 2019 National League MVP Award race, started the season on fire and never looked back, clubbing 14 homers apiece through the end of April to tie the monthly record.

In 2006, Albert Pujols became the first player to hit 14 homers through the end of April, topping Ken Griffey Jr. (1997 Mariners) and Luis Gonzalez (2001 D-backs) with 13 each. The next season, Alex Rodriguez tied Pujols during a terrific opening month that put the third baseman en route to his third American League MVP Award.

May: 17 HR
Barry Bonds (2001 Giants)

Barry Bonds hit a single-season-record 73 homers in 2001, and his pursuit of history really kicked into high gear in May. After blasting 11 dingers in April, Bonds went deep 17 times in the season’s second month. The previous record of 16 was shared by two players who also had historically significant campaigns -- Mickey Mantle in 1956 and Mark McGwire in 1998.

Mantle won the AL Triple Crown in 1956, while McGwire hit 70 homers in 1998, setting the single-season record three years before Bonds surpassed him. Edwin Encarnación came close to tying Bonds in 2014, but he fell one homer short after being held without a long ball on the final two days of the month.

Most through May 31: 28, Bonds (2001 Giants)

June: 20 HR
Sammy Sosa (1998 Cubs)

The 1998 season is best remembered for the home run race between McGwire and Sammy Sosa, but early in the year, it seemed like only one man was in the running to surpass Roger Maris' single-season record of 61, as McGwire outhomered his counterpart 27-13 through May 31. Sosa went off in June, however, socking 20 round-trippers -- not only the record for the month but also the highest total for any calendar month on record.

Sosa homered in five straight games from June 3-8 and had four multi-homer games during the month, including a three-homer effort on June 15. He passed the previous June record -- 15, held by four players (Babe Ruth, Bob Johnson, Maris, Pedro Guerrero) -- with 10 days left in the month. The closest anyone has come to tying Sosa for the June record is Kyle Schwarber, who went deep 16 times for the Nationals in June 2021.

Most through June 30: 39, Bonds (2001 Giants)

July: 16 HR
Albert Belle (1998 White Sox), Mark McGwire (1999 Cardinals)

Albert Belle entered 1998 having earned five straight All-Star selections, but he was left off the ’98 squad after underperforming a bit over the first three months. Perhaps reinvigorated by his time off during the All-Star break, the imposing slugger blasted nine homers in the White Sox first eight games of the second half and finished July with 16 dingers -- only one fewer than he had in April, May and June combined.

McGwire tied Belle in 1999, the year after the Cardinals first baseman’s 70-homer campaign. Before Belle’s July surge in 1998, the previous record for the month was shared by Joe DiMaggio, Hank Greenberg, Joe Adcock and Juan Gonzalez with 15 each.

Most through All-Star break: 39, Bonds (2001 Giants)
Most through July 31: 45, McGwire (1998 Cardinals) and Bonds (2001 Giants)

August: 18 HR
Rudy York (1937 Tigers), Giancarlo Stanton (2017 Marlins)

Giancarlo Stanton nearly became the fifth player in MLB history to produce a 60-homer season in 2017, finishing with 59 and winning the NL MVP Award. His lofty home run total was fueled in part by a monstrous August, during which he hit 18 round-trippers to tie the monthly record Rudy York had set 80 years prior.

A rookie in 1937, York rotated in and out of the lineup over the first four months and hit 12 homers over 180 plate appearances through July 31. However, he started 28 of the team’s 32 games in August and shattered the record for the month, which was previously held by Ruth with 15 in 1929. York almost did it again in 1943, slugging 17 homers in August, and Willie Mays (1965 Giants) and Sosa (2001 Cubs) later hit 17 in a single August as well.

Most through Aug. 31: 57, Bonds (2001 Giants)

September/October (not including postseason): 17 HR
Babe Ruth (1927 Yankees), Albert Belle (1995 Indians)

Already in the midst of a legendary 1927 season, Ruth kicked it up a notch in the final month, belting 17 homers in 28 games to post the first 60-homer campaign in MLB history. In the process, Ruth broke his own September/October record of 11, set in 1921.

Greenberg (1946 Tigers) and Ralph Kiner (1949 Pirates) came one homer shy of tying Ruth before Belle did it in 1995, the year he became MLB’s first player to produce 50-plus homers and 50-plus doubles in a single season. Greg Vaughn (1999 Reds), Bonds (2001 Giants) and J.D. Martinez (2017 D-backs) have since hit 16 homers in September/October.