Pitfalls in charging a supercapacitor from a small solar panel
Any thoughts?


The devil will be in the detail and you have provided little. 


Start with defining your load and the current consumption profile. You also need to state how low the capacitor voltage can drop before your load fails on under-voltage. 
define peak currents in terms of amps and duration - i.e. the full load profile.
Data sheets for everything is needed. Leakage currents for the supercap WILL be an important consideration.
Anything that doesn't support your temperature range is going to make decisions on the circuits ability to fulfill your needs extremely dubious.
Make no assumptions that something "should" work - prove it by due diligence.



  and a 1N4001 diode


I'm unsure about this - I think you need to show your proposed circuit.