Using https://query.yahooapis.com/v1/public/yql with the following request:
select * from weather.forecast where woeid = "..."

When comparing with the yahoo weather page for the same woeid, The values for pressure, visibility, wind speed and windchill in the json data are not accurate both in Fahrenheit and celsius.

The Fahrenheit values returned for those measures are actually the correct Celsius values except for windchill who has the same Celsius and Fahrenheit value.

This was tested with 2 different north american woeid.