How long it takes them to ripen will depend on when they were first planted (and how old they were), the variety (some have short maturities like 55 - 60 days and others long, taking from 70 to even 90 or 100 days to mature and ripen), and of course the weather. Cool and rainy/overcast can certainly slow them down, but at this point, there's not much more you can do but wait. The heat will be on next week with alot of sun, so that should help.

And forgot to mention that yes, sudden heavy rain on tomato plants (especially those close to ripening or ripe) can cause them to split. As a note, some varieties are more prone to splitting and cracking too.