A global study shows that hot weather directly influences mood. Scientists reviewed more than one billion social media posts from 157 countries. Findings revealed negativity increased sharply once temperatures exceeded 35°C. The effect was strongest in poorer regions compared to wealthier nations.
Researchers from MIT and their partners rated emotional tone in posts on X and Weibo. They matched this data with daily weather conditions. Results showed negativity rose 25% in low‑income areas, while in high‑income countries it rose only 8%.
Behavioural Effects of Heat
Hot weather has long been tied to anger and aggression. Past research showed drivers honk more during heatwaves, and journalists use more negative wording. In Greece, many murders occurred on hotter days above 25°C. Historical studies also revealed uprisings peaking during summer months. Hot days have even been connected to increased suicide rates.
Possible explanations include shifts in brain chemistry, lower serotonin, or hormonal changes leading to aggression. Many researchers stress, however, that heat interacts with wider social and economic pressures.
The Outlook for the Future
Climate models suggest a 2.3% global decline in positive sentiment by the end of this century. Vulnerable populations like children and the elderly are underrepresented on social media, so the true scale may be higher.
Experts conclude that societies need to prepare for heat’s emotional challenges. Building resilience against psychological strain must complement physical protection in a hotter world.
