So far no one has produced evidence of glacial activity during the early Paleozoic Era, so we can guess that the climate was generally mild. Although there seems to have been some glacial activity twice during the Precambrian--once about a billion years ago, then again some 750 million years ago--there probably was very little if any ice during the Cambrian, Ordovician, and Silurian periods.
Another reason for thinking that early Paleozoic climates were generally mild is the distribution of fossils. Fossils of the same species are found rather widely spread both north and south, just as if there had been hardly any difference in climate in what is now southern South America and midlatitude Canada. Early Paleozoic fossils recently found north of the Arctic Circle differ very little from those found near the Equator. Again, the evidence points to a generally mild climate from the time Earth's first true cellular organisms arose up until about 300 million years ago, which puts us well into the late Paleozoic.