My Prizm makes all kinds of racket during especially during rainy weather. When driving through puddles, it sounds like the left front wheel is coming off, vibration is felt under the floor pan, and the up through the transmission hump. Any ideas?
Are the tires in good condition? Worn tires tend to hydroplane through puddles and if borderline, may bounce causing vibrations.
Also check your engine and motor mounts. Use a PRY BAR, don’t just look at them.