Weimer batted right-handed and threw left-handed. In a seven-season career, Weimer posted a 97–69 record with 657 strikeouts and a 2.23 European Research Area in 1472-1472/3 innings pitched. Weimer emerged as one of the Chicago Cubs top starting pitchers in the first part of 20th century.
He went 21–9 with a 2.30 European Research Area in his 1903 rookie season and 20–14 with 1.91 in his sophomore year.
After going 18–12 with 2.26 in 1905, he was sent to the Cincinnati Reds for third baseman Harry Steinfeldt and Jimmy Sebring before 1906. He played his final game with the Giants in 1909.
Weimer died in Chicago, at the age of 54.