Approach plates with a snowflake symbol require an altitude corrections for various segments when the outside temperature is below the listed temperatures. You can find the Cold Temperature Altitude Corrections document with a list of Cold Temperature Restricted Airports in ForeFlight under DOCUMENTS > CATALOG > FAA > COLD TEMPERATURE ALTITUDE CORRECTIONS. Once you download the document is is automatically updated each data cycle. We also added an expanded temperature and altitude table with higher resolution than the FAA-provided table.
Image 1. Aspen (KASE) is a Cold Temperature Restricted Airport, which can be determined by the snowflake symbol.