ostoros#27
http://en.wikipedia.org/wiki/Climate_of_Mars#Temperature
"Differing values have been reported for the average temperature on Mars,[15] with a common value being −55 °C (218 K; −67 °F).[16] Surface temperatures may reach a high of about 20 °C (293 K; 68 °F) at noon, at the equator, and a low of about −153 °C (120 K; −243 °F) at the poles.[17] Actual temperature measurements at the Viking landers' site range from −17.2 °C (256.0 K; 1.0 °F) to −107 °C (166 K; −161 °F). The warmest soil temperature on the Mars surface estimated by the Viking Orbiter was 27 °C (300 K; 81 °F).[18] The Spirit rover recorded a maximum daytime air temperature in the shade of 35 °C (308 K; 95 °F), and regularly recorded temperatures well above 0 °C (273 K; 32 °F), except in winter.[19]
It has been reported that "On the basis of the nightime air temperature data, every northern spring and early northern summer yet observed were identical to within the level of experimental error (to within ±1 °C)" but that the "daytime data, however, suggest a somewhat different story, with temperatures varying from year-to-year by up to 6 °C in this season.[20] This day-night discrepancy is unexpected and not understood". In southern spring and summer, variance is dominated by dust storms which increase the value of the night low temperature and decrease the daytime peak temperature.[21] This results in a small (20 °C) decrease in average surface temperature, and a moderate (30 °C) increase in upper atmosphere temperature.[22]"