Correction appended, Jan. 8
A working paper, released by researcher Patrick Baylis at the University of California, Berkeley and reported by the Washington Post, suggests that while people's happiness declines as temperatures rise above 70°F or fall below 50°F, the decline in happiness is stronger as weather gets hotter.
In order to get that conclusion, Baylis evaluated more than a billion posts on Twitter for a connection between temperature conditions in the geographic area in which they were posted and the use of positive and negative words. The method leaves room for error on the individual level, but the aggregate is likely more reliable.
Baylis says his research has implications for economic productivity in the faced of continued climate change. Global temperatures have risen by more than 1.5°F since 1880, a pattern scientists expect to continue in the coming decades. Future changes to temperature due to global warming could have the effect in some areas of "replacing every Saturday and Sunday in a year with a Monday," he writes.
Correction: This story originally mischaracterized how happiness declines with the weather. The study found it declines more strongly in hot weather.