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Planetary Seasons
Color image showing increase in brighter clouds on Neptune.
Scientists say an increase in clouds on Neptune may be due to seasonal changes.

Planetary seasons are caused by two factors: axial tilt and variable distance from the sun (orbital eccentricity).

Black and white image showing the cratered surface of Mercury.

Earth's orbit is nearly circular and so has little effect on climate. It's our planet's axial tilt that causes almost all seasonal changes. When the North Pole is tilted toward the sun, it's northern summer. Six months later the North Pole tilts away from the sun and we experience northern winter.

In the table the equinoxes and solstices are named after the corresponding season in the northern hemisphere. This is the convention that astronomers often use to discuss planetary seasons.

When the north pole of a planet is tilted toward the sun, astronomers call it the Summer Solstice; when the South Pole is tilted toward the sun it is called the Winter Solstice. Nevertheless, the seasons are always opposite in the two hemispheres. On Earth, for example, when it is summer in New York, it is winter in Sydney. On a spring day in Paris, autumn leaves are falling in Argentina, and so on...

Planet     Vernal Equinox Summer Solstice Autumnal Equinox Winter Solstice
  Orbital Eccentricty Spring Axis Tilt (deg) Spring Begins: 2014 Summer Begins: 2014 Autumn Begins: 2014 Winter Begins: 2014
Mercury .21 (one of the most eccentric) 2.11 N/A* N/A* N/A* N/A*
Venus .01 3 N/A* N/A* N/A* N/A*
Earth .02 23.5 20 Mar 2014 16:67 UTC 21 Jun 2014 10:51 UTC 23 Sep 2014 2:29 UTC 21 Dec 2014 23:03 UTC
Mars .09 24 31 Jul 2013 15 Feb 2014 17 Aug 2014 11 Jan 2015
Jupiter .05 3 N/A* N/A* N/A* N/A*
Saturn .06 26.75 TBD* March 2017 TBD* July 2004
Uranus .05 82 1999 2043 2085 2127
Neptune .01 28.5 1963 2003 2043 2084
  • N/A for planets Mercury, Venus and Jupiter because the axial tilt of these planets is insignificant; meaning that while seasonal changes on these planets do exist-- they are often slight and not as severe as they are on Earth. Furthermore, with essentially no atmosphere, Mercury's weather changes are displayed not as storms in the atmosphere, but as wide swings in surface temperature. Venus experiences little temperature variation, due to its thick atmosphere of carbon dioxide, which traps the heat and distributes it around the planet.
  • TBD: NASA's Cassini Mission arrived just after Saturn's northern winter solstice, and this latest extension continues until a few months past northern summer solstice in May 2017. The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere. A complete seasonal period on Saturn has never been studied at this level of detail. The Solstice mission schedule calls for an additional 155 orbits around the planet.
Planet Average Temperatures
Mercury 166.86 degrees Celsius
(332.33 degrees Fahrenheit)
Venus 456.85.86 degrees Celsius
(854.33 degrees Fahrenheit)
Earth 15 degrees Celsius
(59 degrees Fahrenheit)
Mars -63.15 degrees Celsius
(-81.67 degrees Fahrenheit)
Jupiter -108.15 degrees Celsius
(162.67 degrees Fahrenheit)
Saturn -139.15 degrees Celsius
(-218.47 degrees Fahrenheit)
Uranus -197.15 degrees Celsius
(-322.87 degrees Fahrenheit)
Neptune -200.15 degrees Celsius
(-328.27 degrees Fahrenheit)

Last Updated: 17 October 2013

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Last Updated: 17 Oct 2013