We put out a post asking for any weather questions for Schnack's weather blog and our first one came in from a twitter user:
Basically, the difference between cold rain (relatively harmless) and freezing rain (very hazardous) all comes down to the surface temperature. If temperatures at the surface are at 32°F or less, any sort of precipitation, whether it be rain or snow will not melt.
You have to look at the temperature profile with height. All precipitation starts off as snow way up high in the clouds. If temperatures remain at or below freezing from the cloud to the ground, the snow can never melt and therefore the snow piles up at the ground.
Sometimes, temperatures can be at or below freezing just at the surface but a portion of air above the surface can be warmer than freezing. That is when the snow will melt and turn to rain. The rain hits the freezing surface and will turn into ice. This is freezing rain. The ice will coat anything and everything from roads to power lines, trees, and cars. Many accidents/power outages can occur if the freezing rain continues long enough.
If the surface temperature is above 32°F and there is warmer than freezing air above the surface, than you will get just a cold rain. It will not freeze at the ground but will certainly feel cold, especially if temperatures are between 32 and 40 degrees. This poses less of threat but there is the potential for flash freezing if temperatures rapidly drop below freezing after the rain.
Another precip type is if the surface is at or below freezing but there is a pocket of above freezing air well above the surface. This allows the snow to melt into rain and refreeze into sleet or ice particles. This can accumulate and cause slick roads.
If you have any weather questions you are curious about, feel free to email them to firstname.lastname@example.org.