It depends on the length of the extension cord, construction, and gauge.
10awg single conductor THHN can handle 50 amps but when it's in NM-b (house wire/romex) it's 30 amps.
Extension cords can get really hot as they often have the conductor insulation, some packaging material for support, and the outer coating. It also greatly matters if it's 10ft vs 100ft due to resistance.
I've seen extension cords that were used for ACs melt carpets
10awg single conductor THHN can handle 50 amps but when it's in NM-b (house wire/romex) it's 30 amps.
Extension cords can get really hot as they often have the conductor insulation, some packaging material for support, and the outer coating. It also greatly matters if it's 10ft vs 100ft due to resistance.
I've seen extension cords that were used for ACs melt carpets