Temperatures were measured in a small-scale mesocosm (1 m2) experiment during an 8-week period in the summer of 2020, in the Netherlands. The period included a heatwave. Forty mesocosms, each devided in 4 quadrants, were planted with forbs. Temperatures were measured three time a week, during the warmest part of the day, i.e. between 1400 and 1500 h. using an infrared thermometer gun (BOSCH Thermodetector PTD1). Temperatures were mearured near the soil surface at the edge of the mesocosm, near the soil surface between two quadrants in each mesocosm. Within each mesocosm, as well as within the plant canopy. In addition the ambient temperature was measured.