A MEMS hot wire anemometer was designed, simulated, fabricated and tested. The device was of a planar silicon substrate construction measuring wind direction in two dimensions. Wind velocity and temperature were also measured with the same sensing elements on the device. This anemometer formed part of a multisensor incorporating other sensing functions such as humidity and light onto a common silicon substrate compatible with active electronics integration. Of these sensors only temperature, wind speed and direction are presented as the work of this thesis, however integration of each of these sensors within the larger multisensor was a necessary consideration. Also presented are the results of the prototype devices constructed from discrete surface mount components offering device alternatives dependant on application. Simulation and development was aided with Coventorware multiphysics modelling software providing virtual analysis in electrical, thermal and fluidic domains. Fabrication was primarily conducted within the Griffith University fabrication laboratory with a subsequent fabrication run of four wafers in a commercial foundry hosted by Motorola. Packaging options were developed for the silicon die consisting of either conventional chip carriers or application specific fibreglass carriers. Prototype packaging was also developed for the larger complete system incorporating the interface electronics and communications system. Testing was conducted in the laboratory in a controlled environmental chamber and wind tunnel built to calibrate the devices. Laboratory results are reported for the controlled environment response to demonstrate the consistency and accuracy obtained during testing. Wind tunnel testing was conducted both on the carrier mounted die and on the larger self contained system to be deployed into the field trial incorporating all interface electronics and the communications system. Field trial testing was employed to evaluate the devices under continued operation when exposed to typical environmental abuse such as thermal cycling and physical contamination over time. The field trial results present a typical 24 hour period of operation measured against a commercially available weather station mounted in the same location for reference. The results from the laboratory and field trial testing demonstrated the sensor operational and meeting the design requirements, showing a velocity range exceeding 0-30m/s ±10%, directional accuracy of better than 8° and power consumption of 45mW. This was achieved in a die size 42% of that allowable in the design requirements. Fabrication process requirements were largely CMOS compatible and was demonstrated with the integration of a diode on the same silicon die.