Altitude Table
| Altitude Table |
|---|
| Altitude | Temperature (°C / °F) | Cold Modifier | Air % | Air Thinness Modifier |
|---|---|---|---|---|
| 2500 | 10 / 50 | - | 90% | - |
| 5000 | 5 / 41 | +0 | 80% | - |
| 7500 | 0 / 32 | +2 | 70% | - |
| 10000 | -10 / 14 | +4 | 60% | 1+ |
| 15000 | -20 / -4 | +6 | 50% | 2+ |
| 20000 | -30 / -22 | +8 | 40% | 4+ |
| 25000 | -40 / -40 | +10 | 30% | 6+ |
| 3000+ | -50 / x | +12 | 20% | 8+ |
Any creature not native to high-altitude conditions, and not using specialized equipment, traveling at an altitude between 10,000 and 20,000 feet, is subject to thin air conditions. Once above 10,000 feet, all affected creatures must succeed a DC 10 + the air thinness modifier (see Altitude Table) Constitution saving throw at the end of each hour or suffer from Altitude Sickness until cured.
Breathing creatures can become accustomed to thin air conditions by spending a month or longer in these conditions. Once adopted, they no longer suffer the negative conditions of high altitudes. This adaptation is lost if you spend more than 2 weeks outside of these conditions.
Low Temperature
Temperatures drop rapidly at higher altitudes, with water starting to freeze at 7,500 feet and above. The average creature can function normally without special gear until an altitude height of 5,000 ft. Once above 5,000 ft, each hour, all affected creatures must succeed a DC 10 + the cold modifier (see Altitude Table) Constitution saving throw at the end of each hour or gain one level of exhaustion.
Creatures native to cold climates, with immunity or resistance to cold, or wearing protective gear (e.g. a thick coat, gloves, masks, and the like) automatically succeed this saving throw.
Altitude Sickness
Any creature affected by the Altitude Sickness condition will suffer a -2 penalty to all Intelligence-based checks and saving throws. Additionally, they cannot regain spell slots, remove exhaustion levels, or regain Hit Dice and Hit Points when resting.
The condition can be cured for 12 hours by casting a Lesser or Greater Restoration spell or fully cured by spending 1d4 days resting at an altitude below 10,000 feet or in a similarly high oxygen environment.
Extreme Cold
Any creature affected by the Extreme Cold condition will have its speed reduced by half and have -2 on ability checks, attack rolls, and saving throws.
