Temperature Along the Balloon's Path

A weather balloon drifts across a valley. The air temperature at ground position $(x, y)$, with $x$ and $y$ measured in kilometres east and north, is modelled by

$T(x, y) = x^2 y + 3y^2$

in degrees Celsius. The balloon's position at time $t$ hours is

$x(t) = 2t + 1, \qquad y(t) = t^2 - 1$

The temperature the balloon reads is therefore not a direct function of time: time moves the balloon, and the balloon's position sets the temperature.

How fast is the temperature the balloon reads changing at the moment $t = 2$? Give the exact value in degrees per hour.