This article provides a detailed overview of both factors influencing habitual physical activity, and relationships between such activity and health in the elderly. Current cross-sectional data from the Nakanojo Study, which we have been carrying out since 2000, indicate substantial associations between the overall health of participants, and both the year-averaged daily step count and the year-averaged daily duration of effort undertaken at an intensity >3 metabolic equivalents (MET). In men, the extent of health is associated more closely with the daily duration of activity >3 MET than with the daily step count, whereas in women the association is closer for the step count than for the duration of activity >3 MET. In both sexes, the threshold amount of physical activity associated with better health is greater for physical than for mental benefits: >8000 vs >4000 steps/day and/or >20 vs >5 min/day at >3 MET, respectively. In other words, physical health is better in those spending at least 20 min/day in moderate walking (at a pace of around 1.4 m/s [5 km/h]) and a further >60 min of light activity per day. In contrast, better mental health is associated with much smaller amounts of deliberate physical activity. Both the intensity and the total volume of physical activity are influenced by meteorological factors, particularly precipitation and mean ambient temperature. Activity decreases exponentially to about 4000 steps/day as precipitation increases. Excluding the influence of rainfall, the daily step count peaks at a mean outdoor temperature of around 17 degrees C; above and especially below such readings, physical activity decreases as a quadratic function of temperature. Seasonal changes in the microclimate should thus be considered when designing interventions intended to increase the habitual physical activity of older adults. Based on these findings, we are now developing preventive tactics that should contribute to health promotion, disease prevention and thus a reduction in medical expenses for elderly people.