A fifth person died on the Slovak side of the mountains, which straddle the border between Poland and its southern neighbour.
A major rescue operation was launched on Thursday afternoon, with helicopters scrambled, and search teams and firefighters sent to the Giewont peak in the Tatras.
Earlier in the day, Polish media reported that at least a dozen people had been struck by lightning in the Giewont area.
Prime Minister Mateusz Morawiecki was expected to travel to southern Poland in the wake of the tragedy, government spokesman Piotr Müller said on Twitter.
A 15-metre steel cross at the top of the Giewont peak often draws lightning, state news agency PAP reported.
Standing at 1,894 metres, Giewont is by far the most popular tourist destination in the area. It is about a three-hour hike from the mountain resort of Zakopane.
The weather in the region was sunny on Thursday morning, but then worsened dramatically in matter of minutes.