Yes, there are multiple flights from Toronto to Adirondack Regional Airport for under C$ 636. The cheapest flight booked recently is on Multiple Airlines for just C$ 555, but on average you can expect to pay C$ 839.
There are no direct flights from Toronto to Adirondack Regional Airport, but Cheapflights can provide you with all the information you need to find the fastest route with the fewest stops.
Temperatures around the 28 °C's can be experienced in July. The weather in Saranac Lake is hotter than in Toronto. Plan for potential changes in flight availability as peak weather approaches in this location.