The cosmic background radiation is pretty weak stuff these days. What was it like when the Earth/Solar system was formed?
An exact answer would depend on a detailed model of the Universe’s expansion, but for a rough back-of-the-envelope estimate: The Universe at the time of the Solar System’s formation was about 2/3 as old as it is now. So the CMB would have been about 1.5 times hotter. Which is still pretty puny.