Navajos, for example are only certified in MODERATE icing and that's only if every part req in the POH (antenna shields included) is fitted and working.
Few propellor driven aircraft, including transport category turboprops, are certified for more than Moderate icing, the next step being Severe, which is unpredictable and includes freezing rain and drizzle.
It's unfortunate the industry hasn't come up with anything piston to replace the C400 series/PA31's. If you're carting anything more than 5 adults total and gear, you're going to have to consider 8/10 seats.
I think its more a pitty the turbine versions such as the PA31-T3 (T1040) and the less know Emb-821 Caraja (EMB-820 Navajo turbine conversion) were not produced in more numbers. The Caraja also may not be certified outside of South America but had a 500kg increased MTOW with 550hp PT6A-27/-34. This allowed about 220Kt cruise and 600m field performance, MTOW 3600kg BEW around 2300kg.
If you can find a T1040 for sale they are usually around $500000US.