3 Answers

Due to the Earth's axial tilt, winter lasts from the winter solstice (typically December 22) to the vernal equinox (typically March 20), while summer lasts from the summer solstice (typically June 21) through to the autumnal equinox (typically September 21).

Due to the tilt of Earth's rotation relative to the Sun and the ecliptic plane, summer is December to March and winter is June to September. September 22 or 23 is the vernal equinox and March 20 or 21 is the autumnal equinox.

So when it is summer in the Southern Hemisphere, it is winter and spring in the Northern Hemisphere

If funds permit, you can have summer all year round by travelling from northern hemisphere to south. For the last few years I have travelled from Europe to Aus/ NZ  leaving Dec, returning end March.

SUMMER