Considerations and What to Typically Expect
Late April into May are busy. With spring, we usually have an abundance of water from snow melt off offering a wide range of trips to choose from. It is primarily better white water for the white water enthusiast. And is the only time you can justifiably plan on some of the rivers such as the Machias and St. John.
In early June the waters begin to warm with the onset of spring. Variable and dropping levels reduce the choices of rivers to plan trips on.
July and August seem to be the prime months clients choose for trips. The rivers to plan on are more limited and these rivers have more traffic and volume of people than at other times of the year. Water temperatures are at their warmest and comfortable for swimming.
Fall is my favorite season in Maine. The days are mild and nights are cool. The foliage is beautiful in late September into October. The water temperatures are still warm and you will find the dam controlled rivers generally running at moderate and enjoyable levels.
With rain water levels can change and offer a variety of rivers to choose from at anytime of year. You just cannot plan on a number of rivers following the typical spring run off. MaineGuiding takes this into account and can change rivers if one more enjoyable and suitable to the group is available to run during the scheduled time period. We would not need to, but it is nice to have the options if it opens up.
Except for fall and winter it is bug season in most places in Maine; typically not what I call bad or very bothersome, except in certain spots and at certain times. They are here and can be dealt with in a comfortable manner with a little "bug dope" (insect repellant) or mosquito netting if they are found to be bothersome.
Viewing animals is always by chance. Eagles and osprey are pretty much a given to see on the eastern rivers and very common on the other rivers. The St. Croix has several eagle nests that can be viewed from the river. Typically at least one will be active with young.
The Machias has an Osprey nest that been producing young most every year. Moose can possibly be seen on any of the rivers but it is most common to sight them on the western and northern rivers; the St John, Allagash and varies branches of the Penobscot and other rivers.
A lot of history is associated with Maine rivers. From the days of the rivers being paths and routes of the native peoples, to early expeditions and military routes such as Benedict Arnold's failed attempt to attack Quebec. Then the rivers and waters were fought over and controlled by the lumber barons during the heyday of timber harvesting. Those days are lost, but not forgotten, and there is history of these activities still to be found within the woods. A trained eye can see and recognize the permanent changes brought about during the logging days, be it just pins in the rocks or remnants of dams and sighting of blasted rocks that were in the way.
The Allagash has the most intact history of the logging days, with a man-made cut allowing water and logs to be diverted into the Penobscot watershed to Bangor rather then flowing north along the Allagash, into the St. John and into Canada. There are locomotives and various other equipment that is still intact and can be viewed. Due to nostalgic history and status, the Allagash seems to draw the most attention.
The Allagash consists of mostly lake paddling, beautiful sights and abundant wildlife. It is patrolled and maintain by park rangers. The camp sites are well kept and maintained with picnic tables and outhouses at most camping sites. The use is relatively high and seeing other campers and some motor boats is to be expected. With lakes come the possibility of winds that can make it an easy short day paddle, if we have a tail wind, to a long arduous paddle if we encounter a lot of strong head winds. There is a possibility of being wind bound 'till the wind subsides to a safe level to travel again. 7-8 day trip
The St John, is a beautiful scenic river, the most remote in Maine with limited access. It gets it prime use during the spring run-off of snow melt. The spring is the only time you can reasonably schedule a trip. But as weather goes, following a good rain the river rises and offers a supreme trip. The St. John river is also one of the most ecologically significant areas in Maine. 7-8 day trip
The Penobscot and the Penobscot watershed offer a number 
of trips. There is the Upper West Branch, which is runable throughout the season and offers mild and gently moving water. This can include a side trip into Lobster Lake with beautiful beaches and decent fishing. This trip is recommended for those apprehensive of white water and or with small children. Moose sighting are very common on this trip. 4- 7 day trip
The East Branch of the Penobscot offers challenging white water and many beautiful views. This river is lightly traveled and used, partly because there are a number of portages. The work is worth it if you are physically fit and enjoy white water and a more remote atmosphere. The camp sites are not maintained but general well kept and clean. They typically lack outhouses. Instead they have pit toilets and or are self shoveled. The river is dammed, controlled, and usually can be run through out the season. 3 to 5 days
There is an offering of extending the East Branch. We can start in the Allagash waterway and proceeding through Telos Cut into the Northern end of Baxter's Webster stream. This brings you into the head waters of the East Branch. Doing so offers an additional opportunity to include some hiking or back packing within the park. This would be for those more physically fit and those that are into a more of a challenging trip. Extended East Branch trip: minimum of 6 days. Recommend: 7 plus hiking and backpacking day(s).
The Machias is the primo of the Down East rivers for the white water enthusiast. There are many take out and put in options allowing a number of variations to trip offerings. In general it is a white water river where skills are needed, with some portaging and a number of more challenging rapids. 3- 8 day trip
You never can go wrong with the St. Croix river.
This beautiful river flows between Canada and Maine. The camp sites are plentiful, well dispersed and well maintained. The river is dam controlled and runnable through out the season. The St. Croix is an excellent and enjoyable river for the novice to experienced paddler. It starts off gently with plenty of options and opportunity for instructions and getting familiar with paddling. It is a general mix of moving water and scattered easy runnable rapids throughout the trip. 
The rapids increase in difficulty some but is nothing a novice with motivation and proper instruction will not enjoy running. The river section has an option of three to four days of paddling with an option of paddling the lakes above to extend the mileage and distance of the trip. Minimum 3 days, recommend 4-5 days river with considerations of 1-2 lake days and 3-9 day trip 