Yes, Airtop works very well in summer.
Convection cooling keeps constant delta-T between hot-spot and ambient air for given power (actually deltaT slightly decreases as temperature is rising due to improved radiation).
Furthermore, both CPU and GPU in Airtop do an excellent job in autonomous thermal management.
Assuming ambient temperature of 400C in summer rather than 250C in winter.
CPU thermal headroom in winter: 1000C-250C=750C
CPU thermal headroom in summer: 100C-400C=600C
We can see in the example that in summer the thermal headroom of Airtop is 80% of what it was in winter.