You can get the latest weather (Maximum and Minimum temperatures per Sol or Martian Solar Day) on Mars from the Phoenix Mars Lander delivered to your desktop from the Phoenix lander currently on Mars.
Download: Phoenix Mars Weather Gadget
The Phoenix Mars Lander is a Martian lander (not a rover like Mars Pathfinder) designed to look for evidence of water or ice under the surface of Mars. Instead of roaming around the surface of Mars looking for water evidence – the Phoenix lander will dig below the surface to look for water or ice. Matter a fact, today the Phoenix Mission Team announced they may have found ice – aka frozen water! That’s awesome.
The Phoenix Mars Weather Gadget is updated regularly as soon as the weather data is downloaded* from the Phoenix Mars Lander.
*In some cases due to technical reasons, weather data may not be available on a daily basis. For example: I believe today is Sol 25 but the Phoenix Mars Weather Gadget is reporting weather data from Sol 22.
You can get the latest on the Phoenix Mars Mission from their website here or the NASA website here. You can follow them on Twitter as well.