The manufacturer's datasheet for the exact part you have will have temperature ranges for both storage and operation. CMOS devices generate very little internal heat, so you cannot rely on insulation alone to protect it from extreme low temperatures.
Beyond that, as above, most reliability issues come from the physical environment - solder quality, pc board and device pin surface contamination, etc. There are spray-on conformal coatings in a small can similar to hair spray. Acrylic is good, urethane is better.
Because coefficients of expansion for the pc board and the device package are different, temperature cycling, especially rapid changes in temperature (called thermal shock), can lead to board and trace cracking.
Is the board going to be exposed to the elements (rain and snow), or in a protective enclosure?
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