The optimal temperature range for life on Earth to thrive is around 20°C (68°F). Research shows that animals, plants, and microbes living in air and water have overlapping thermal ranges centered near 20°C, which appears to be the most stable and efficient temperature for biological processes across many forms of life
. Biological processes tend to increase with temperature up to this point, then rapidly decline when it gets warmer. Temperatures above 20°C are increasingly suboptimal and can lead to decreases in species richness, genetic diversity, and tolerance to environmental stresses like low oxygen in marine species
. The molecular properties of water in cells likely make 20°C pivotal for efficient cellular function. For humans specifically, survival is generally possible within a broader range, roughly from 4°C to 35°C, depending on humidity and other factors
. Comfortable indoor temperatures for humans are typically between 18°C and 24°C, with recommendations for vulnerable groups to have a minimum of about 20°C
. In summary:
- Optimal for most life forms: ~20°C
- Human survival range: Approximately 4°C to 35°C
- Comfortable indoor temperature for humans: 18°C to 24°C
This 20°C optimum is significant because it aligns with maximum biodiversity and biological efficiency, while temperatures above this threshold tend to reduce ecosystem complexity and species survival
