A ventilated shield for measuring outdoor air temperature and humidity (e.g., on a weather station). Three parts that must be bolted together using four 2 inch 6-32 machine screws with four nuts and washers - four 20 mm spacers are needed between the fan and cap (can be made from vinyl tubing slipped over the screws). Forced ventilation can achieved using any 40mm x 40mm x 10mm DC axial fan (a larger 20 mm thick fan can also be used). Initial testing was done with ADDA AD0405HB-G70 (5V, 6.7 CFM). The barrel is designed to house a Humidity and Temperature Sensor - SHT15 Breakout - from Sparkfun Electronics, but other sensors could be employed. The entire shield should be mounted to a horizontal pipe using a U-bolt (1 3/8 inch internal spacing)