Not a direct answer for your specific case, but a few things to consider for similar situations:
Big local events. If there’s a big fair, exhibition, tournament, match, concert, festival or anything that could draw large crowds, it can use a lot of hotel capacity, and the less local capacity the more chances you may have to travel quite a bit to find accommodation, or pay outrageous prices.
I’ve seen the case in Europe, where professional exhibitions in mid-size cities such as Basel or Geneva can lead to a complete saturation of all hotels, with people who haven’t booked in advance having to face a one-hour commute for attendees. I’ve already had to stay in Mulhouse or Zürich to attend a fair in Basel! In rural areas with even less hotel capacity, this can extend much further even for relatively small events.
Some such events can be quite long (a week or more), or sometimes be just a single day (which will affect hotels for a night or two).
Important holidays in the country/region of “catchment” (the one people come from). For places visited a lot by US citizens for instance (which may drown locals in many neighbouring places), some dates like the 4th of July (especially if it falls nicely next to a weekend), New Year’s Eve, or sometimes the full “festive season” can lead to a significant increase in bookings.
For those two, since those are usually planned in advance, a simple guide is to check availabilities and prices in the intended locations during the intended timeframe. If you see few availabilities or high prices, that’s already a hint. Compare with timeframes before and after if necessary.
Another risk is weather-related disruption (and other significant events such as volcanic activity or terrorism), which is a lot more unpredictable, but usually more limited in scope (usually hotels close to large airports, which may have to host lots of stranded passengers). Not much you can do about those if it happens, but I would be surprised if that happened in that area, though Operation Yellow Ribbon shows it can happen.
One other factor to take into account in areas which have widely different numbers of visitors along the year (with a very well delimited peak season), is that many facilities may be closed for the off-season (or, sometimes worse, are open but with limited service). But again, checking availabilities for the prospective dates should give you a good idea of what you can expect.
These days lots of tourism-related operators have a lot more flexibility in their booking terms. You could take advantage of that to book flexible stays to cover your whole holiday, and then adjust your reservations if your plans change.
Which brings us to another point you may not have considered: booking in advance will often yield much better prices than last minute bookings, even if there’s plenty of availability (though that’s probably more true for big chains rather than smaller independent hotels). The price you see today for those dates may not be the price you’ll see the day before…