The API is returning "unknown" for some values for Montreal, Canada

For my city (Montreal, Canada), the API is returning "unknown" for current_observation.icon and current_observation.weather, and "http://icons.wxug.com/i/c/k/unknown.gif"; for the current_observation.icon_url for a couple of weeks or so.

I spot-checked against a few other Canadian cities and they're getting complete results (at least for those fields).