Massachusetts, unlike many states, does not seem to publish GIS data for water quality classifications.  So we have no fancy maps here.

That's not to say MA doesn't publish a lot of water quality information that is potentially useful to folks seeking wild trout.  It does. 

Check out the map below and the list that follows.  Massachusetts is divided into 27 major watersheds.  We've labeled them "Cold" if they include at least SOME streams which the state regulations designate as "cold water".  Download the "State Regs" document and look up the watershed you're interested in.  From the table and maps provided, you should be able to figure out if the specific stream segment you want to fish is cold water or not.*  Most streams in the far west are cold water.  As you head east, warm water streams start to predominate.

We've also provided the latest "Watershed Water Quality Assessment Report" (WWQAR) for each of the watersheds marked "Cold" in the list.  These provide a treasure trove of qualitiative information.  Check out the "USE ASSESSMENT - AQUATIC LIFE USE" sections for relevant stream segments.  They'll give typically give you results from fish sampling done in the area.

1 Hudson River Basin - Cold
2 Housatonic River Basin - Cold
3 Farmington River Basin - Cold
4 Westfield River Basin - Cold
5 Deerfield River Basin - Cold
6 Connecticut River Basin - Cold
7 Millers River Basin - Cold
8 Chicopee River Basin - Cold
9 Quinebaug River Basin - Cold
10 French River Basin - Warm
11 Blackstone River Basin - Cold
12 Ten Mile River Basin - Warm
13 Narragansett Bay/Mount Hope Bay Drainage Area - Cold
14 Taunton River Basin - Warm
15 Boston Harbor Drainage Area - Warm
16 Charles River Basin - Warm
17 Nashua River Basin - Cold
18 SuAsCo River Basin - Cold
19 Shawsheen River Basin - Warm
20 Merrimack River Basin - Cold
21 Parker River Basin - Warm
22 Ipswich River Basin - Warm
23 North Coastal Drainage Area - Warm
24 South Coastal Drainage Area - Warm
25 Buzzards Bay Coastal Drainage Area - Warm
26 Cape Cod Coastal Drainage Area - Warm
27 Islands Coastal Drainage Area - Warm

* The tables don't generally list "designated use" stream by stream.  Instead, they list the largest stream in a given region which is cold water habitat, and then assert that the higher order tributaries are included unless listed as an exception.  So if you're looking at a headwaters stream, in general you'll need to figure how it flows into the major streams within the basin.