Herewith drawing from maxim:
As you can see, it is very small. There is no readout in the field, but that does not worry me. If it is cold in the field, it is cold. Tough.
To quote the Maxim datasheet:
"the high-capacity Thermochrons/Hygrochrons allow 8192 readings with time intervals from 1 second to 273 hours. Additionally, the Hygrochron allows for simultaneous temperature and humidity logging and offers selectable resolution settings."
Back home I download the data using a little gizmo you can also buy from Maxim, import into Excel, and make a graph, thus:
One blue line is a simple temperature logger, the other (C2) is a combined temp/RH unit. Red is RH. (My colour choices.) The Temp unit sits inside my pack; the temp/RH unit sits outside (to sense RH as well). As you can see, it got down to about -6 C one night. That's not that cold of course.
What the Thermocron cannot tell you is wind-speed. On night 2 it got down to about -5 C, but the wind-speed was over 100 kph. Yep, that was "When things Go Wrong" :-)
Doing this sort of thing requires two trade-offs. The first is weight: these i-Buttons are trivial in weight, but a Brunton data logger is not. The other trade-off or effort is that you have to set up the Maxim software, which is simple but not 100% trivial. Works for me though.