Can you turn on the air conditioning?
'Condizionata' — 'con-di-tsyo-NA-ta'. Five syllables; stress on the fourth.
Ask in summer or in hot weather when the taxi feels stuffy and you need the air conditioning switched on.
'Accendere' means to switch on (literally 'to light'). 'L'aria condizionata' is air conditioning. Its opposite is 'spegnere l'aria condizionata' (to turn off the AC).
Può abbassare la temperatura?
Can you lower the temperature?
Asks for a cooler setting rather than switching AC on.
Può aprire il finestrino?
Can you open the window?
'Finestrino' is the car window; alternative to AC.
Fa troppo caldo qui.
It's too hot in here.
States the problem and lets the driver respond.
All modern Italian taxis are equipped with air conditioning. In summer (especially in southern Italy) it is essential. Some older drivers keep windows open instead — a polite request is always respected.