You can catch
Mantine- Surf at Undella bay
Mantyke- Surf at Undella bay
Walrein- Surf at Undella bay
Tranquill- Route 6, 7, Dragon Spiral Tower(only in winter)
Unfezant- Route 6, 7, Dragon Spiral Tower
Palpitoad- Route 8, Icirrus City, Sekka Swamp
Shelmet- Route 8, Icirrus City, Moor of Icirrus
Stunfisk- Route 8, Icirrus City.
Everything you find in summer you also find in Autumn and Spring... There is no summer only Pokemon.