It's air temperature that's recorded. This can be quite difficult to do, trying to ensure that direct heat from the sun doesn't influence the thermometer. Even when the thermometer is shaded by a well-ventilated housing, (a 'Stephenson Screen') the interior can be heated up by the sun shining on it, giving a false result. Some of the other problems regarding the location of a thermometer are discussed
here
As Catso infers, leaving a thermometer in direct sunlight can send it off the scale!