Usage patterns
〈場所〉でにわか雨が降るa sudden rain shower falls in 〈場所〉
A sudden shower fell in the park in the afternoon.
にわか雨に遭うto get caught in a sudden rain shower
I got caught in a sudden shower on my way back from shopping.
にわか雨に降られるto be caught (soaked) by a sudden rain shower
I didn't have an umbrella, so I got soaked by a sudden shower.
にわか雨がやむa sudden rain shower stops
After a while, the sudden shower stopped.