Drought conditions.

[ShaunG]

As everyone is aware Massachusetts and large parts of New Hampshire were hit with a pretty bad drought this Summer. My question is how should I expect this to effect sap production of the trees?

[maple flats]

I'm just guessing, but I think unless it was so dry that the trees defoliated, it will depend far more what mid fall thru next maple season brought for moisture, both rain and snow. Then you need good freeze thaw cycles.
If the trees partially or heavily defoliated the sugar will be well below your typical %. Again, this is just my opinion with no scientific data.

[DrTimPerkins]

As Dave noted, there is little scientific evidence. In terms of sap production, weather during the season is the dominant factor there. For sap sugar content, there are a large number of influences, drought is one of them. Dry conditions DURING the season are not good, but dry conditions in the summer and fall prior to the sap season also tend to reduce sap sugar content. Hot summers and hot extended fall periods are also not especially good. However again, it is very difficult to predict that a single factor such as drought will have an impact, and even more difficult to say just how much effect it might have. In any case, no sense fretting too much about things you don't have any control over. Collect sap, boil it into syrup, and bottle it .... at the end you'll know how good a season it was.