Because Australia is a medium-sized continent, separated from polar regions by the Southern Ocean, it is not subject to movements of frigid polar air during winter, of the type that sweep over the continents in the northern hemisphere during their winter. Consequently, Australia's winter is relatively mild, with less contrast between summer and winter temperatures than in the northern continents–though the transition is more dramatically marked in alpine regions of Australia and places of substantial elevation. Seasonal highs and lows can still be considerable. Temperatures have ranged from above to . Minimum temperatures are moderated.