Here is a small chart to use when characters are traveling in wilderness. Bird in the Hand scenario brings in more detailed rules for finding shelter. If you do not know where a good shelter is your travel will get slower and there is a risk of having to sleep in the open.
The RAW rules state wearing suitable local clothing permits a character a grace period of their CON in hours before exposure sets in. The chart below shows the RAW rules for effect of being exposed to temperature ranges. The wonderful Hex Crawl rules in the scenario Bird In the Hand situated in the Monster Island enhance if you try to rest without proper tent or lean-to you risk exposure and there is no recovery of fatigue or natural healing.
In the jungle you will be wet most of the time either thru torrential afternoon rains, constant wetness of everything or the rivers. If you try to rest overnight without first drying yourself and without a fire and lean to or tent for the night – you are likely to get more and more fatigued. So if you try to sleep in a tree to avoid ground level predators (and encounter the higher order predators above) you are likely to not get rest unless you find a nice nest or build a tree house but how to keep warm there..
So even if there is no check required – there is no recovery of fatigue or natural healing unless you are sheltered.
.and the link to pdf is here