After having began with the home club JYP Jyväskylä, Summanen made his first steps in the SM-Liiga in 1981 when he joined Reipas Lahti. The following season, he joined Ilves Tampere and blossomed, scoring 45 goals and totalling 60 points in 36 games. This caught the attention of the North American scouts, and the Edmonton Oilers made him the 125th overall pick of the 1982 NHL Entry Draft. Summanen failed to translate his SM-Liiga numbers to the NHL. On March 10 1987, he was traded to the Vancouver Canucks for Moe Lemay. He didn't do better there, and was back to Finland in 1988, where he set big numbers with Tampere for the next two seasons (respectively 81 and 70 points), which earned him back-to-back Veli-Pekka Ketola Trophies, before joining HPK Hämeenlinna. He would then play for TPS Turku, Jokerit Helsinki and SC Bern before retiring from playing in 1995, after having won the gold medal of the 1995 World Championship with the Leijonat.
He also coached the Finnish National Team for the 2004 World Cup of hockey, leading the team to a second place finish. However, Summanen's very abrasive style led to his firing. Even though the team was being succesful on the ice, Janne Niinimaa left the team due to "personnal conflicts with the coaching staff". He also had tense relationships with Timo Jutila, general manager of the team.