Combine those observations with the fact that the seasons are reversed in the Southern Hemisphere, and you're well on your way to figuring this mystery out -- a tilt in the Earth's axis.
(the seasons; are reversed; L:in the Southern Hemisphere) (you; 're; well on your way to figuring this mystery out -- a tilt in the Earth's axis)
the seasons you
are reversed 're
L:in the Southern Hemisphere
well on your way to figuring this mystery out -- a tilt in the Earth's axis