Lower temperature
Let's verify
As per Boyles law
[tex]\\ \rm\Rrightarrow V\propto \dfrac{1}{P}[/tex]
As per Charles law
[tex]\\ \rm\Rrightarrow V\propto T[/tex]
[tex]\\ \rm\Rrightarrow T\propto \dfrac{1}{P}[/tex]
So
At higher altitudes lower the pressure so lower the temperature