In this study, we investigated summer microclimate elements (air temperature, relative humidity, and wind speed), as well as visitors' thermal sensation, space choices, and activities, at four representative sites in Heilongjiang Forest Botanical Garden. Site 1 was a paving square located at the park entrance, with a few trees and benches. Site 2 was a lakefront area with trees, shrubs, and herbaceous plants, which also had pavilions and benches. Site 3 was a woodland landscape with a canopy density of 0.93. No passive recreational facilities were provided at this site. Site 4 was a flower garden containing herbaceous flowerbeds. With the aim of exploring associations among individuals' thermal sensation and visitor populations in different space categories, we conducted measurements of meteorological variables, survey interviews, and observations of human activities. At each of the four sites, a Kestrel 4500 weather meter was used to measure air temperature, relative humidity, and wind speed. The measurements were taken from 09:00 to 17:00 over a period of 3 d. During the measurements, surveys were conducted at each site to collect information on visitors' thermal sensation. A total of 500 questionnaires were distributed, of which 471 (463 being valid) were returned. Observations of visitor activities were recorded for 20 min per hour during the site measurements. The results showed that outdoor microclimate parameters played important roles in visitors' thermal sensation. Among these microclimate parameters, air temperature was the most influential, followed by relative humidity and wind speed. In summer, the visitors to Heilongjiang Forest Botanical Garden generally felt more comfortable with cooler air, higher air humidity, and a stronger breeze. Visitors in different garden sites were not equally sensitive to changes in thermal comfort conditions. Visitors in the square area with a large amount pavement were most sensitive to changes in thermal comfort conditions. Visitors in the herbaceous flower garden area were the next most sensitive. In the waterfront area containing leisure facilities, the correlation between the number of visitors and change in thermal sensation was minimal. In the woodland area, there was essentially no association between the number of visitors and the change in thermal sensation. Therefore, shade was the dominant factor influencing visitors' selection of recreational space in summer. Scenery and functionality of landscapes could also potentially decrease people's sensitivity to a change in thermal comfort conditions, thereby affecting their space choices. In addition, visitors' age and visiting frequency were also associated with their thermal comfort. Considering that the elderly tend to visit the park more frequently than people of any other age category, their thermal comfort needs in summer should be of primary concern to landscape designers. For example, the elderly tend to choose park spaces with more leisure facilities.