As I recall, for every 1000 foot increase in altitude, temperature in F. goes down 5.5 degrees until you reach the dew point, when it then goes down 3.5 degrees per 1000 feet.

This is a rule of thumb and can be affected by other conditions.

Still, going from sea level to 13,000 feet could drop the temperature as much as 71.5 degrees, ignoring the dew point. So that nice beach day of 72 could go to near zero.

You will need something more than that Hawaiian shirt. . .