Approach plates with a snowflake symbol ( ) require 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 > FAA > WINTER OPERATIONS > COLD TEMPERATURE ALTITUDE CORRECTIONS. Once you download the document 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.