In Maine the best whale watching dates are from mid-to-late April, to mid-to-late October. It is during these months... ...that the waters in the Gulf of Maine are at their warmest and provide an excellent feeding ground...ut regardless, you will likely find late spring and early fall to be a very relaxing time to see Maine whales, with less crowds and shorter lines! Although Maine best whale watching dates are when the weather in Maine is at its nicest, don't be fooled... ...