Can you explain some differences between air and surface temperatures, and why that difference matters?

Darrel Jenerette, professor in the botany and plant sciences department Department of Botany and Plant Sciences and director of UCR's Center for Conservation Biology: Surface temperature is measured using a radiometric approach ¾ basically an infrared thermometer. It is measured by handheld devices, drone cameras, planes, and satellites. It is a measurement of the outer layer of a material: rooftops of buildings, the top layer of soil, or exposed leaves. Air temperature is measured at a height of 2 meters above the ground.

It is important for plants, as knowing surface temperature is a good measure of the actual leaf and has consequences for photosynthesis as well as water loss. More water loss through the stomata cools the leaves. It's also important for people to know about surface temps in that they are an indicator of the overall thermal environment and are components of the total heat load on a person.

Compared to air temperature, surface temperature is more spatially and temporally variable. For both, there is a lot of ongoing research trying to uncover how the thermal environment affects people. Not surprisingly, it's complicated but no matter how you measure it, over 100 degrees Fahrenheit is hot.