Never mind, apparently this is normal behavior. The server attempts to mimic the temperatures of the actual IRL island, thus thermals are significantly affected. This isn't easy to replicate in the editor, hence why I thought it was a bug. This is further compounded by the rather sudden shift in Thermal view performance, while we would instead expect a more gradual change in thermal performance. Perhaps this is something to consider?
In any case, since this is expected behavior from I&A scripting, it's best to close this bug report.
Case closed, pack it up, boys. Go home.
Its effects are manageable, I'm sure we'll all be used to it sooner or later.
(In other news, Tanoa and Livonia are largely unaffected. Join us there!)