There are different causes for image noise, and one of those causes is the temperature of the image sensor.
Astronomers cool their digital image sensors. Pro astronomers use liquid nitrogen (-346° to -321°) under presure to minimize thermal noise when making long exposures, some exposures as long as 8 hours. Amateur astronomers use digital cameras specially for astrophotography that use electrical cooling systems. Hereis one that can keep the image sensor at 40°c below ambient air temperature:
Orion Parsec 10100C Color Astronomical Imaging Camera
In winter the cold can seriously shorten the charge life of batteries but the cold rcan educe thermal noise, while hot summer air tempertures can definately add to the earlier onset of DSLR thermal noise.