I've used many laptops over the years. There's only been one that didn't have problems with overheating in heavy, or sometimes even light to moderate, usage situations. In my experience, the vast majority of laptops have insufficient cooling capabilities to function as a cluster node.
That said, I frequently use that one laptop at 100% load for extended periods of time and have been doing so for around three years now, and it hasn't had any problems the others experienced (RAM failure, battery failure, fan failure, and sometimes just unexpected shutdowns without any obvious hardware failure).
You suggested A/C and a big fan as a possible solution. If your laptop stabilizes at 120 degrees in a 70 degree room, it'll stabilize at roughly 110 degrees in a 60 degree room (or 120-x degrees in a 70-x degree room). It would take a pretty cold room for that to work though. The big fan doesn't help much as it likely won't move a noticeable amount of additional air through the laptop. Proximity and direction will affect the accuracy of that statement.
An additional fan blowing air directly into the intake(s) or sucking air directly from the outlet(s) of your laptop will definitely help though. If you move twice as much air through your laptop, the difference between the temperature at which your laptop stabilizes and room temperature will be roughly half what it would be without the additional fans. (In the previous example of a 120 degree laptop in a 70 degree room, the temperature difference is 50 degrees. Blowing twice as much air through the laptop, the difference will be 25 degrees, bringing the laptop's temperature down to 95 degrees. Three times as much air would yield a third the temperature difference, and so on.)