Tazz,
There are engine icing conditions and airframe icing conditions. It is possible to get engine intake icing on some types well above zero (depends a lot on the intake design.) Likewise on the pitots, because of the pressure drop in the airflow around them, causing a reduction in the temperature from ambient.
Airframe icing will tend to start at one particular place for each airframe. Often the first place you will see it is on the wipers, the front of skids or antennae. You will have to ask around for the acquired knowledge on your particular aircraft. Airframe icing builds up fastest in temperatures close to zero, because of the size of droplets and the time it takes them to freeze as they run over the airframe. You can build up ice very quickly if you are in the wrong conditions, affecting the performance of your rotors (main and tail), affecting balance, aircraft weight, ability to autorotate etc. Shedding of ice from the rotors can damege other parts of the aircraft. In very cold weather, you may get less icing, but its best not to try it!
If your rotorcraft flight manual says to avoid icing conditions, then the best plan is to do just that. Dont fly where icing conditions are forecast - especially freezing rain. If you do enter icing conditions, turn round and get out again.
I knew a colleague when I was in the Navy who flew a Sea King into icing conditions. There was no way out (in cloud in mountainous region, no radar). They ended up pulling maximum contingency power at best rate of climb speed, and were still descending fast. They were lucky enough to exit the cloud at the base without hitting the ground , but it could easily have gone the other way!
Most helicopters dont like icing - very few have significant airframe/rotor icing protection. If you dont want to scare yourself, stay out of the clouds in Winter!