Ice dams are exactly that, dams. As snow on the roof melts, they hold the water back from gutters or running off the roof's edge.

If your shingles are not in good repair or if you don't have a good impermeable barrier beneath them, which is standard on most roofs but also wears over time, water  that backs up under the roof shingles will get into your house.

Steeper roofs deter the problem better than those with less pitch.

If it has been more than 10 years since you got a new roof and you see an ice buildup along your gutters, check inside, if you can, about 10 feet back from your roof's edge and see what water might leak onto.

Just as water will flow through holes in a dam, it will find and flow through a rip or worn spot in a roof's barrier.

If it gets through attic insulation it can damage your ceiling. 

You can have a contractor remove the ice from your roof's edge or cut channels in the ice to allow melting snow to drain. Do not pay more than a couple of hundred dollars.

Installing heating cables along the roof's edge is probably not cost effective. If you haven't seen this problem before, it's definitely not worth it.

If you do get roof-edge heating cables, make sure they are attached to a switch with a timer or a light to tell you when it's on. Just like any other electrical heating device, roof cables are expensive to operate.

Whatever you choose, get a written contract that the work has been done on a certain date in case water gets in later and damages your ceiling or posessions.

Have a clear understanding with your insurance company what is covered. The contractor will probably only be responsible for limited damage. Have a written understanding with him or her. 

Use a contractor with references, either from friends or from a website such as servicemagic. If you can find a contractor in Hopkinton or a neighboring town with good references, that's probably best.

You'll know they aren't going anywhere and they'll want to do an especially good job near their home base.

For do-it-yourselfers

Make sure the ladder is firmly grounded, not on snow that will allow the ladder to slip or give way.

Don't damage your roof. The ice will be as hard as rock. You wouldn't saw on top of your car or hit it with a sledgehammer or an ax. Think about that before you use those tools on your house. Heat and a flat bar are probably best for homeowners.

Don't set your house on fire. Torches, heating irons and high-temperature heat guns can heat wood or surrounding materials to their ignition point.

This is really a job for professionals who are insured, use safe practices and are used to working in harsh conditions.

The 'Hail Mary': If you want, you can try filling a stocking with a softball-size portion of sodium chloride (ice melt) and heaving it onto the ice dam to melt channels that water can drain through. Some people tie twine onto the stocking so they can pull it to the spot they want. Twine hanging off your house is better than water through the ceiling.

If the Hopkinton area gets a heat wave and the ice melts quickly it should be no problem. If we have typical early spring/late winter sunny days and cold nights and your house has ice dams and an older roof, you may get water damage if you don't take preventive measures.