Ambient temperature shall be measured in shadow. Sensor under direct sunshine will give wrong data, to avoid this, use weather and radiation protection shield for ambient temperature sensor.
Solar Radiation Shield for Ambient Temperature Sensor PT100, PT1000, DS18B20 etc.
Solar Radiation shield
Stainless steel, mounting bracket
Cable Gland PG9 size or box
Dowels and screws for wall or pole mounting
Dimensions: App. 190mm x 72mm x 72mm (130mm from the wall/pole)
Note: Not including temperature sensor