La Crosse Technology WS-9016U Instruction Manual page 18

For every sudden or significant change in the air pressure the weather icons will
update accordingly to represent the change in weather. If the icons do not change,
then it means either the air pressure has not changed or the change has been too slow
for the indoor weather station to register. However, if the icon displayed is a sun or
raining cloud, there will be no change of icon if the weather gets any better (with
sunny icon) or worse (with rainy icon) since the icons are already at their extremes.
The icons displayed forecasts the weather in terms of getting better or worse and not
necessarily sunny or rainy as each icon indicates. For example, if the current
weather is cloudy and the rainy icon is displayed, it does not mean that the product is
faulty because it is not raining. This simply means that the air pressure has dropped
and the weather is expected to get worse but not necessarily rainy.
Note: After setting up, readings for weather forecasts should be disregarded for the
next 12-24 hours. This will allow sufficient time for the indoor weather
station to collect air pressure data at a constant altitude and therefore result in
a more accurate forecast.
Common to weather forecasting, absolute accuracy cannot be guaranteed. The
weather forecasting feature is estimated to have an accuracy level of about 75% due
to the varying areas the indoor weather station has been designed for use in. In areas
that experience sudden changes in weather (for example from sunny to rain), the
indoor weather station will be more accurate compared to use in areas where the
weather is stagnant most of the time (for example mostly sunny).
If the indoor weather station is moved to another location significantly higher or
lower than its initial standing point (for example from the ground floor to the upper
floors of a house), disregard the weather forecast for the next 12-24 hours. By doing
this the indoor weather station will not mistake the new location as being a possible
change in air-pressure when really it is due to the slight change of altitude.
WEATHER TENDENCY INDICATOR
Working together with the weather icons is the weather tendency indicators (located
on the upper left and right side of the weather icons). When the indicator points
upwards, it means that the air-pressure is increasing and the weather is expected to
improve, but when indicator points downwards, the air-pressure is dropping and the
weather is expected to become worse.
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