This is a cropped portion of a data plot showing the solar wind speed and density from December 1999 - December 2000. Please click on image for full view. In that full view, you can see that wind speeds remain between 200-800 km/s. It's possible, but rare, for solar wind to reach speeds above 800 km/s. All data was collected by the SWOOPS instrument.
Courtesy of NASA, ESA and LANL (the principal investigator of SWOOPS)