How do summers differ between Earth's hemispheres?

Each year, Earth's Northern and Southern hemispheres cycle through four seasons, including summer. While at first glance you might assume summers should be similar on both sides of the world, climate experts reveal that they differ quite significantly.

Firstly, Northern and Southern hemisphere summers occur at different times. Earth's axis is tilted 23.4 degrees relative to its orbit around the sun, causing each hemisphere to be oriented toward the sun at different times throughout the year. Northern summers span from late June to late September, while Southern summers run from late December to late March.

Secondly, the duration of Northern and Southern summers varies. On average, Northern Hemisphere summers are 4.5 days longer than Southern Hemisphere summers due to Earth's slightly elliptical orbit around the sun. This difference arises because Earth moves more slowly during aphelion, the point at which our planet is farthest from the sun, resulting in a shorter distance covered from late June to late September in the Northern Hemisphere compared to late December to late March in the Southern Hemisphere.

Thirdly, Northern summers tend to be hotter than Southern summers. A 2015 study in the journal Climate Dynamics found that, when averaged over all domains and latitudes, Northern summers are 7.83°F (4.35°C) warmer than Southern ones. This disparity can be attributed to factors like the Northern Hemisphere's larger landmass compared to water, and the way solar heat gets distributed through air and water.