Below are suggestions for optimal placement of a weather station. Farm locations vary to such a degree that it is not possible to meet a formal set of guidelines in all locations. However, as much as is feasible at each location, weather stations are placed according to National Weather Service (NWS) and weather station manufacturer specifications.

Variations in siting NEWA weather stations may result from the following:

• objectives of the user
• commodity type (i.e. orchard vs. field)
• farm structures
• cable length limits
• radio frequency limits

Placement of NEWA weather stations should come as close as possible to meeting NWS and manufacturer specifications. The weather data collected and delivered via NEWA remains highly valuable for crop production and IPM forecast applications.

For orchards, vineyards and fields it is optimal to place the station in an open area and not within the planting. If placement is near the edge of the orchard, vineyard or field, make sure that tree or trellis height is well below the wind and rain gauges. Protect weather instruments from spray applications because this may damage the sensors or cause erroneous readings.

Official NWS Regulations on Siting Temperature Sensors and Precipitation Gauges:
Steve Anderson of the National Weather Service writes, "As you well know, not every location will be able to conform to (the NWS) rules and regulations, especially in urban areas. It is our job to see that each NWS site conforms as best as possible to these regulations."

Temperature sensor siting:
The sensor should be mounted 5 feet +/- 1 foot above the ground.
The ground over which the [radiation] shelter is located should be typical of the surrounding area.
A level, open clearing is desirable so the thermometers are freely ventilated by air flow.
Do not install the sensor on a steep slope or in a sheltered hollow unless it is typical of the area or unless data from that type of site is desired.
The shelter should be no closer than four times the height of any obstruction (tree, fence, building, etc.)
The sensor should be at least 100 feet from any paved or concrete surface.

Precipitation (rain) gauge siting:
The exposure of a rain gauge is very important for obtaining accurate measurements.
Gauges should not be located close to isolated obstructions such as trees and buildings, which may deflect precipitation due to erratic turbulence.
To avoid wind and resulting turbulence problems, do not locate gauges in wide open spaces or on elevated sites, such as the tops of buildings.
The best site for a gauge is one in which it is protected in all directions, such as in an opening in a grove of trees. The height of the protection should not exceed twice its distance from the gauge.
As a general rule, the windier the gauge location is, the greater the precipitation error will be.

Leaf wetness sensor siting:
NEWA suggests that you place leaf wetness sensors in the open area with the weather station. This protects the sensor and cables from pruning, spraying and harvesting activities. Leaf wetness sensors of the plastic grid type should be placed facing north and angled 45 degrees from horizontal.

For additional help, watch this tutorial video from Weather Underground.

RainWise MKIII SP weather stations and radio transmission:
The weather station radio transceiver is designed to transmit signal more strongly in a down-hill direction. For this reason, place the station uphill from the receiver location, if at all possible.
Radio signal transmission is best with:

• Clear line of sight (no trees, buildings, etc.).
• Few to no metal-frame structures in vicinity.
• 90 degree angle between radio wave and wall behind which receiver is located.
• Open ground cover as opposed to asphalt.

Additional sources of information:
Campbell Scientific, Application Note Code 4-S, Weather Station Siting and Installation Tools (pdf)

Citizen Weather Observer Program (CWOP) Weather Station Siting, Performance, and Data Quality Guide. Version 1.0, March 8, 2005. (pdf)

Carroll and Gibbons, 2009