Quick Answer

Station placement determines your data quality more than any other single factor. Temperature sensors go in a ventilated radiation shield at 1.25–2 metres height over natural ground cover — not on a south-facing wall, not above a driveway, not under a tree. Wind sensors mount at 10 metres ideally, but the highest clear point you can manage works for relative measurements. Rain gauges need open sky with no overhanging branches and protection from wind-induced under-catch. This Tutorials guide covers WMO-derived placement rules adapted for residential stations.

What This Guide Covers

We cover the WMO and CIMO guidelines that define professional siting standards, how to adapt them for residential and hobbyist contexts, specific placement rules for each sensor type, mounting techniques, common placement mistakes with real-world impact on data quality, and how to document your station metadata for data sharing networks. If you plan to contribute data to CWOP or Weather Underground, placement quality directly affects whether your data passes their quality checks — as discussed in the observation standards reference.

Why Placement Matters More Than Hardware

I have seen £500 stations produce worse data than £100 stations simply because of where they were mounted. A Davis Vantage Pro 2 bolted to a south-facing brick wall above a concrete patio will read 5–8 °C too high on a sunny summer afternoon. A cheap Fine Offset station in a properly shielded position over grass will give you readings that correlate within 0.5 °C of the nearest airport METAR.

The sensor does not know it is in a bad location. It faithfully reports whatever temperature, wind, or rainfall it measures in its immediate microenvironment. If that microenvironment is a heat sink, a wind shadow, or a splash zone, the data is accurate for that spot but useless for representing actual weather conditions.

Temperature Sensor Placement

The Radiation Shield

The single most important piece of equipment for accurate temperature measurement is the radiation shield (or Stevenson screen). This is a louvred enclosure that:

  • Blocks direct sunlight from heating the sensor
  • Blocks reflected radiation from the ground
  • Allows natural air circulation around the sensor
  • Protects against rain and precipitation on the sensor

Most consumer stations include a basic radiation shield. The quality varies enormously. Thin plastic shields with poor ventilation can still produce solar heating errors of 2–3 °C. Fan-aspirated shields eliminate this problem by actively drawing ambient air across the sensor, but they require power and add a moving part that can fail.

Height and Surface

  • Height: 1.25–2 metres above ground level. This is the WMO standard observation height. Higher readings miss ground-level cold pooling. Lower readings are overly influenced by surface heating.
  • Surface below: Natural ground cover (grass, soil) for a radius of at least 3–4 metres around the sensor. Avoid concrete, asphalt, gravel, decking, or any artificial surface that stores and re-radiates heat.
  • Distance from buildings: At least 4× the height of the nearest building. A one-storey house (5 m) means 20 m away. This is rarely achievable in residential settings — get as far away as practical.
  • Orientation: In the northern hemisphere, mount the radiation shield so its access door faces north. This prevents the door from being opened toward the sun during maintenance.

Common Temperature Placement Mistakes

  1. Mounting on a south-facing wall. The wall absorbs solar radiation all day and re-radiates heat, creating a warm microclimate. Your temperature readings will be consistently 3–8 °C above actual air temperature on sunny days.
  2. Placing above a paved driveway. Asphalt and concrete reach 50–60 °C on sunny days. Even at 2 m height, the radiated heat significantly biases temperature readings upward.
  3. Under a tree canopy. Trees trap heat at night (blocking radiative cooling) and shade the sensor during the day. Nighttime minimum temperatures can read 2–3 °C too warm, while daytime maxima may read slightly cool.
  4. In a wind shadow. Temperature sensors need natural ventilation. Placing the shield in a wind-free zone behind a building or fence reduces air circulation and increases measurement error.

Wind Sensor Placement

Height

The WMO standard for wind measurement is 10 metres above open, level ground. For residential stations, very few operators can achieve this. Mount the wind sensor at the highest clear point available — above the roofline, on a mast or pole.

The key principle: wind speed increases with height, and obstructions create turbulence. A sensor at 3 m height behind a house will measure gusty, directionally chaotic wind that bears little resemblance to the actual wind flow. The same sensor at 6 m on a pole above the roofline gives much more representative readings.

Obstructions

The "2× distance" rule: the sensor should be at least twice the height of any obstruction, measured from the top of the obstruction. A 6 m house means the sensor should be at least 12 m away horizontally, or high enough above the house to clear its turbulence zone.

On rooftops, mount the anemometer on a 2–3 m mast to get above the turbulent boundary layer that forms at the roof surface. The edges and peaks of roofs create severe turbulence.

Direction Alignment

The wind vane's north pointer must be aligned to true north (not magnetic north). Use a compass and apply your local magnetic declination correction. A 10° alignment error means every wind direction you report is 10° off.

Rain Gauge Placement

Open Sky Rule

Rain gauges need an unobstructed view of the sky from the gauge rim to at least 45° above horizontal in all directions. Nearby buildings, trees, or fences act as both wind barriers and rain shadows.

Wind Effects

Wind is the biggest source of rain measurement error. Wind flowing over the gauge opening creates an upward pressure differential that deflects raindrops away from the gauge. At 4 m/s wind speed, a standard gauge under-catches by roughly 5%. At 8 m/s, under-catch can exceed 15%.

Mitigation: use a wind shield (Alter shield) around the gauge, or mount the gauge at ground level surrounded by a non-splash surface like turf or gravel. Ground-level mounting eliminates wind-induced under-catch but introduces splash risk.

Level and Clear

The gauge must be level (use a bubble level during installation) and clear of overhanging branches, wires, or structures that drip. Even a single branch overhanging the gauge can double the apparent rainfall during tree-drip events.

Pressure Sensor Placement

Barometric pressure sensors are typically inside the station console or in the outdoor sensor array. Placement is less critical than for other sensors because pressure is relatively uniform over small distances. Key considerations:

  • Altitude matters. Set the correct station elevation in your software so that sea-level-corrected pressure (QNH/SLP) is calculated accurately. A 10 m altitude error causes roughly 1.2 hPa pressure error.
  • Avoid drafts. If the pressure sensor is indoors, do not place the console near an air vent, open window, or door. HVAC-induced pressure fluctuations can create artificial readings.
  • Temperature stability. Pressure sensors have temperature coefficients. A sensor in direct sunlight or near a heat source may drift.

Documentation and Metadata

If you share data with weather networks, accurate metadata is essential. Document:

  • Latitude and longitude to 4 decimal places (±11 m accuracy)
  • Elevation above sea level in metres (use a GPS reading or topographic map)
  • Sensor heights (temperature, wind, rain gauge above ground)
  • Surface description (grass, concrete, rooftop, etc.)
  • Obstructions (nearest building, trees, fences — distance and height)
  • Any non-standard installations (fan-aspirated shield, wind shield on gauge, etc.)

Networks like CWOP and the data sharing platforms use this metadata for quality control. Incorrect elevation is the most common metadata error and causes pressure-based quality checks to flag your station.

Common Mistakes Summary

Mistake Impact Fix
Temp sensor on south wall +3–8 °C bias on sunny days Move to freestanding mast over grass
Wind sensor below roofline Erratic direction, reduced speed Mount above roofline on mast
Rain gauge under tree Over-count from drip, under-count from interception Move to open ground
Wrong altitude in software Persistent pressure bias Re-measure with GPS or topographic data
Wind vane not aligned to true north Systematic direction error Realign using compass + declination
No radiation shield +10 °C or more in direct sunlight Always use at least a basic louvred shield

Related Reading

FAQ

What if I cannot meet WMO placement standards? Most residential stations cannot. The goal is to get as close as practical. Even imperfect placement produces useful data if you document the limitations and understand the biases. A station on a rooftop with a known wind-speed multiplier is still useful.

Should I move my station to a better location even if it disrupts my data record? Yes, if the current location is producing clearly biased data. Document the date and nature of the move. Most analysis tools can handle a station relocation as long as it is documented. Bad data in a long record is worse than a shorter record of good data.

How do I know if my placement is affecting my data? Compare your readings against the nearest airport METAR station. Consistent biases (always warmer, always calmer, always drier) suggest placement issues. The Station Data Sanity Checks guide provides a systematic comparison methodology.

Do all-in-one stations (like the Ecowitt WS90) have placement compromises? Yes. An all-in-one unit forces all sensors to share one location. The optimal height for a wind sensor (10 m) is not ideal for a temperature sensor (1.5 m) or rain gauge (ground level). All-in-one stations trade accuracy for convenience. If accuracy is paramount, use separate, individually placed sensors.