More than 60% of full-time employees who experienced summer fatigue reported that the condition negatively affected their professional duties [1].
The findings highlight a growing concern regarding how extreme seasonal heat disrupts workforce productivity and mental focus in Japan. As temperatures rise, the physical toll of heat exhaustion translates directly into operational inefficiencies within the corporate sector.
According to a survey conducted by Mynavi among full-time employees aged 20 to 59, approximately 38.1% of respondents experienced summer fatigue during 2026 [1]. While other reports suggest higher percentages of the general population felt the effects, the specific data for full-time staff ranges between 38.1% and roughly 40% [1], [2]. Among those who suffered from the condition, 64.4% said it impacted their work [1].
The symptoms reported by workers primarily centered on a loss of drive and a decline in mental acuity. Approximately 40% of those experiencing summer fatigue said they struggled with a lack of motivation [1]. These qualitative declines in performance were echoed by the survey participants.
"Concentration dropped and work efficiency declined," said a man in his 40s [1]. A woman in her 20s said she lacked the motivation to work because she had no appetite [1].
These individual accounts illustrate a broader trend where physical ailments caused by heat lead to a measurable dip in output. The data suggests that summer fatigue is not merely a personal health issue but a systemic business challenge that affects a significant portion of the workforce.
Mynavi emphasized the need for corporate intervention to mitigate these effects. The company said that promoting flexible working styles, and improving the workplace environment, are essential to support health maintenance and the achievement of stable results [1].
“64.4% of full-time employees who experienced summer fatigue said it impacted their work.”
The correlation between seasonal heat and diminished productivity suggests that 'summer fatigue' is becoming a recognized operational risk for Japanese companies. By quantifying the impact on motivation and concentration, the data provides a business case for implementing heat-mitigation strategies—such as flexible hours or enhanced cooling—to prevent systemic productivity losses during peak summer months.
