The radiation symbol looks a bit much like an old fashioned computer tape reel, but I doubt there is much that can be done about that. Maybe lightning the outer circle to the stroke weight of the skull and bones will help, along with lengthening the fan blades.

Making the ring a little larger in the biohazard symbol might make it read better.

Very nice skull and bones. The teeth are going to be reduced beyond recognition at text sizes but the rest should hold up.

I quite often see a rain cloud (cloud with slashes underneath) on the local weather reports instead of an umbrella. Does Unicode specify “umbrella” for that position or just “rain” (or are you making this set up without regard for established Unicode symbols)? You’ll need a black cloud with a lightning bolt dropping from it for thunderstorms, if you don’t have one already. I’ll have to defer to people who live with snow for an opinion on the snowman vs. snowflake controversy.

Back up to your first two rows, the planetary symbols seem just fine but some of the others seem a touch too light. I’m a bit rusty on which of those is which, though.