2 - Activity rhythm on hot (> 25°C) and cold (< 25°C) summer days.

2 - On hot summer days with an effective ambient temperature (T_e) > 25°C, marmots are less active and retreat in their burrows, especially at noon. On colder days, the activity is evenly distributed over the day. The lower heat pressure is less a consequence of the air temperature, than the screening of the radiation by clouds, as can be seen by the small difference of air tmperature and T_e on colder days.
Sunrise and sunset are marked by arrows. (Figure after Türk & Arnold)