A question about capacitor type and temperature limits
Operating temperature range


The Operating Temperature Range is the temperature range over which the part will function, when electrified, within the limits given in the specification. It is the range of ambient temperatures for which the capacitor has been designed to operate continuously. Largely the formation voltage sets the high-temperature limit. Higher formation voltages permit 
higher operating temperatures but reduce the capacitance. The low-temperature limit of an electrolytic capacitor is set largely by the cold resistivity of the electrolyte. The higher cold resistivity increases the capacitor’s ESR 10 to 100 fold and reduces the available capacitance.

The electrolyte is a complex blend of ingredients with different formulations according to voltage and operating temperature range. The principal ingredients are a solvent and a conductive salt – a solute – to produce electrical conduction. 

The common solvent is ethylene glycol (EG) and is typically used for capacitors rated –20 ºC or –40 ºC. Dimethylformamide (DMF) and gammabutyrolactone (GBL) are often used for capacitors rated –55 ºC. Common solutes are ammonium borate and other 
ammonium salts.


Storage Temperature Range


The Storage Temperature Range is the temperature range to which the part can be subjected unbiased, and retain conformance to specified electrical limits. It is the range of ambient temperatures over which the capacitor may be stored without damage for short periods. 

For long periods of storage 
keep capacitors at cool room temperatures and in an atmosphere free of halogen gases like chlorine and fluorine that can corrode aluminum. Storage temperature ranges are from –55 ºC to the upper limit of the operating-temperature ranges.

Sources:

Capacitor Selection Guide - KEMET (.PDF)

Aluminum Electrolytic Capacitor Application Guide - Cornell Dubilier (.PDF)