Weak Radio reception in the rain?

Up until now I have been quite satisfied with the basic radio in my 2013 Prius v Two. Actually figured out the USB port as well as the Random files and folders settings. BUT....
Today we have had an all day winter rain. I immediately noticed 2 things. First the roof has almost no sound insulation! Rain on the roof was LOUD! Then I discovered some of the radio stations I had been listening to for over a week were now nearly lost. Reception was probably a tenth of what it was in dry weather. Should I blame the weather? Could there be a problem with water interfering with the external antenna? Even stations that were very close and should have had a strong signal would at times have interference. Is this common with Prius v's? Is there an antenna upgrade?
One other question... When I am in Trip display.... showing the MPG bars what are the tiny symbols that sometimes appear at the bottom of the bars? Appears to be symbols for Regen braking. How should I interpret them? Good thing? Bad thing? thanks.