If one applies the real world rules of 3, then the following cases can be used by the GM..
3 minutes without air=death
3 hours without shelter (exposed to extreme weather)=death
3 days without water=death
3 weeks without food=death
Using those real-world examples, The GM should be able to interpret some negative impacts as a character moves closer to the death option of each condition.
Example: 3 days without water will kill a human (real world), but before that, there will be notable consequences,
Day one, a little dizziness, some lack of dexterity, disorientation,
Day two, significant dizziness, disorientation, concentration. Stamina, strength and Dexterity issues.
Day three, No concentration (no spell use), Significant; Stamina, Dexterity, strength, intelligence, wisdom across the board.
Day four, Death save days, if passed, then keep layering on the reductions in Int, Str, Wis, Dex, Stam...
Day Five or more, Death Save with lowered stats, and is still passed, again lower all stats and start heading the character to a coma state.
this of course only a suggestion, a GM can make their own rules.