It isn't steam, it is condensed water vapor in air (fog or a cloud). The temperature depends on a few things but generally somewhere around 35 degrees C based on info I just looked up. The water being pushed out of the tower is not water from the steam-generation system used to power the electric turbines. That steam is not usually released except in emergency (the steam is recovered as liquid and reheated to make new steam, in a big circle of use).

Instead, what happens is that the used steam from driving a turbine (now only hot water) is pumped to a radiator of sorts (some sort of closed unit that has air pass over it) located at the base of the tower. Air passing over this radiator heats up (takes heat form the hot water in the radiator, cooling that water more). the cool water is sent back to be made back into steam.

To help cool this air taking the heat from the "radiator", a spray of cold water is typically used. This spray is released near the top of the tower and descends down over the upflowing hot air (cold water is used as a counter flow to the rising hot air to help cool it faster). The water is usually taken from a nearby river or other similar water body. it is "fresh" water, different water from the water used by the electricity-generating system.

Because of this water spray, the hot air gets saturated (maximum humidity), and because maximum humidity decreases as temperature of the air drops, the water vapor condenses into droplets, making a fog or a cloud. This is what we see leaving the plant tower. The water in the discharge fog is not radioactive and it is not all that hot.