Are these temperatures harming my iMac?

Apple, Intel and other semiconductor providers would all prefer to avoid the costs associated with recalls and repairs arising from inadequate or mis-designed cooling.

Or… For the technical answer… Look up TDP, and then look up the specific semiconductor parts involved, and then look up the specified thermal limits for each. intel has these thermal specs available, as do most other vendors.

As you get going into more detail and learning more particularly about processors and processor design here, you’ll also learn more about how parts of processors and cores will power down to reduce power consumption and reduce heat, and how some processors and some system designs can sustain boosted clock rates (and generated heat) longer due to their cooling designs, and how the processor base clock specifications can be a better means to compare performance as boost can drop off rather quickly as heat builds. Among other details.

But more simply put, Macs fried under normal usage would be Bad For Revenues. Thermal design mistakes here are rare. There are some seemingly-foolhardy people using add-on tools to reduce fan speeds and decrease cooling from what Apple and Intel have designed. I’d not recommend that.

Nope.

As thermal limits are approached, you’ll get increased cooling, then performance throttling, and then hard (protective) shutdown as thermal limits are reached.