we have an average wind speed of 9-10 mph @ 100 ft for the last 3 months on our farm, can we make a 250 kw turbine project feasible?
We are in Ontario, Canada and looking at a Net Meetering program.

The rule of thumb I've heard is that a site with an average wind speed of 10 mph or less usually does not have enough wind to justify putting up a turbine, even a small-scale one.

Also, when you're assessing the wind resource at a site, it's best to have more than just a couple months data. This is because winds often vary significantly season to season. (It might look like you have enough wind to make a project financially viable if you only look at the windy season, but if you average the wind over the whole year the same site might not make sense.)

If you're interested in finding out more about assessing the wind resource on your property, Windustry has some resources that might be of help:
Small Wind Systems: Know Your Wind Resource
Wind Basics: Know Your Wind
Information on Wind Prospecting

Would be tough; you have to get up higher.

100 foot is pretty low for a 250kw turbine to be operating at anyway. If you move up to 150 feet I bet you can get around 12-13mph which would be better but even that isn't a whole lot of wind.