1988-89 Hershey Impact bring indoor soccer to the greater Harrisburg area with their first season in the American Indoor Soccer Association, finishing in 4th place with a 21-19 record. They faced Canton, top seed in the playoffs and regular season with a 25-15 record and were swept in the first round by the Invaders 14-8 and 5-0. Canton went on to win the league title, defeating the Chicago Power three games to one.

1989-90 Hershey Impact finish third in the four team American Division with a 19-21 record. They faced the second place Atlanta (eventually Kansas City) Attack and were swept again in the first round by scores of 13-10 and 13-9. Canton again won the league title, defeating the Dayton Dynamo three games to one.

1990-91 This is the year the league changes its name from AISA to The National Professional Soccer League. The change didn't help the team as the Hershey Impact missed the playoffs, falling to fourth place with a 19-21 record. Only the 3-37 New York Kicks kept them out of the basement. The Chicago Power went on to sweep the Dayton Dynamo in three games. Hershey and New York folded after the season.

1991-92 Under new ownership the Harrisburg Heat are born, signing several Hershey players and area soccer fans are treated to a second place finish with a 24-16 record behind the Canton Invaders. They scored 547 points while giving up 462, providing them with the second best offense and third best defense in the league. However, the Heat were swept in the playoffs by the third place Detroit Rockers by scores of 19-12 and 16-8. The consolation was that these same Rockers upset the defending champion Chicago Power two games to one before winning the league championship against the Canton Invaders three games to two.

1992-1993 The Heat fell to fourth place in a seven team division with a 22-18 record. The improvement in offense to 597 points made them the third best scoring team in the league; it was offset by a defense which gave up 556 points, only seventh best in a league which expanded to 14 teams. In the opening round of the playoffs the Heat swept Baltimore by scores of 16-3 and 22-9. They then lost to Cleveland by scores of 15-16, 20-18 OT and 16-7. Kansas City defeated Cleveland three games to two for the championship.

1993-94 The Heat again finish fourth, behind Baltimore, Cleveland and Buffalo with a 19-21 record. The offense dropped off to 557 points (8th in league) while the defense became more porous, giving up 585 points (7th in league). Again the Heat faced Baltimore and history repeated itself with a Heat sweep by scores of 21-9 and 13-7. The same was true in the second round as they lost to the eventual league champion Cleveland Crunch for a second straight year despite taking the opening game 14-13. Cleveland came back with scores of 15-10 and 21-10. The Crunch defeated St. Louis for the championship three games to one.

1994-95 The Heat finish second in the six team American Division with a 23-17 record. With an improved offense scoring 594 points (5th in league) supported by a defense which gave up 526 points (5th best), the Heat looked forward to the playoffs. After defeating Baltimore in three games by scores of 17-4, 15-17 OT and 14-6 they finally got past Cleveland by sweeping the Crunch 17-7, 24-18 and 16-12 for the American Division Championship. But the promise of league championship glory ended when they were swept by the St. Louis Ambush 19-9, 18-8, 12-7 and 14-11.

1995-96 The improvement by one game to 24-16 made this the best Heat team to date, but it was only good enough for a third place finish behind rivals Cleveland and Baltimore. Their 604 points on offense gave them a tie with Baltimore for the fourth most potent offense in the 13 team league and the 516 points allowed on defense was an improvement over last year but still only good enough to be 5th best in the league. It proved to be an omen as Baltimore "Spirited" them from the playoffs by scores of 16-11 and 7-6. Baltimore took Cleveland to four games before bowing out. It took six games before Cleveland "Crunched" Kansas City for the championship.

1996-97 The league expanded to 15 teams with the addition of Toronto and Philadelphia. The intrastate rivalry proved to be good for the Heat. Though they slipped to a 22-18 record it was good enough for them to take the East Division by 2 games over Baltimore during the regular season. The decline in offense to 523 points (10th best) was offset by a stingy defense which surrendered a league best 457 points. Earning a first round bye put them against Cincinnati in the second round, who the Heat swept by scores of 11-9 OT and 13-12. History repeated itself for the Heat as Cleveland knocked them out of the playoffs in four games by scores of 8-11, 19-13, 14-17 and 12-14. However, history would not hold true for Cleveland as the Kansas City Attack returned the favor from last year, defeating the defending champs in a four game sweep for a championship of their own.

1997-98 The Heat slipped a game to 21-19, finishing 5 games behind intrastate rivals Philadelphia. The offense scored 530 points (7th best) during the season while the defense gave up 518 (tied for 6th). The Heat defeated Cincinnati in the first round with scores of 14-12 OT, 5-27 (worst playoff loss ever), and 18-13. In the second round Milwaukee quickly dispatched Harrisburg by scores of 4-19 and 11-18. Milwaukee went on to defeat St. Louis for the Championship in five games..

1998-99 The Heat remained at 21-19 for a second straight year behind intrastate rivals Philadelphia. The offense sometimes struggled under new coach Richard Chinapoo, scoring only 478 points (9th best) during the season even with the addition of Gino DiFlorio (4th in NPSL in Lifetime Scoring) while the defense improved by alloing only 498 (6th). The Heat defeated Montreal on the last game of the season to gain another above-500 season, only to lose to the Impact in the playoffs. Montreal went on to lose to the Cleveland Crunch, who went on to win the Championship..