The temperature gradient may be a straight line or can be stepped where the type of insulating layer changes.
Condensation can occur at some point along this temperature gradient where the combination of temperature and humidity forces water vapour to condense, releasing latent heat of condensation.
As the temperature inside the insulation fluctuates, perhaps because of exercise, there may also be a humidity gradient. This is caused by different materials, with different breathabilities, impeding the movement of water vapour inside the garments.
It is worth remembering that every layer of fabric impedes breathability. Those that are more windproof have a greater impedance to water vapour. Condensation is more likely to occur at these 'barriers'.