For all the seized wing guys asking about ice and helicopters, a personal experience from decades past, a "learned about flying from that":
Was flying a Bell 412 on top to a destination with forecast and actuals of clear (CAVU) but darkness was approaching. Locally we were above an undercast layer of undetermined depth. OAT was approx -25C, we were cruising at 10,000' and felt that we could expect minimal ice accumulation in cloud so elected to start a slow descent down through and avoid a steeper arrival over destination. We also expected to reach clear air shortly.
Less than a minute after starting our descent into cloud(less than 500' from the tops), the icing rapidly increased from nil to light to moderate. We tried to climb back on top but Vbroc and Max Q only gave us a ROD of around 100 fpm.
We declared a MAYDAY, got ATC assistance, and eventually broke out in a very high rate descent. Enough ice was (luckily) shed before hitting the trees that we were able to get to destination.
We had been lulled over previous years of flying the 212 in northern, winter conditions to feeling comfortable with minimal (trace/light) ice exposure and the 212's ability to get back out if we encountered something we didn't like. As we learned, the newer rotor designs are horribly unforgiving.
My point: very few helicopter pilots will risk any icing conditions unless there is absolutely no other choice.