Here is the full list of all 20 Snowball Saves Summer achievements.
Start a new game.
Save Sunny Tundra.
Save Glacier Beach.
Save the Toy Factory.
Save Mt. Meltdown.
Save Summer!
Collect all Costumes.
Collect all Trails.
Collect all Golden Snowflakes.
Beat the game in less than 2 hours.
Unlock all the secret levels.
Have 999 coins or more in your inventory.
Travel more than 1,000,000 units of distance in the air.
Travel more than 25,000 units of distance in the water.
Travel more than 50,000 units of distance on land.
Defeat more than 1,000 enemies.
Beat the game without losing more than 9 lives.
Level up any one of Snowball's stats.
Ask Santa for help.
Complete a Krampus Run (New Game+).