Long distance transport of various types of pollen has been recognized for decades. The Aerobiology Laboratory at the University of Tulsa has been studying the long distance of mountain cedar (Juniperus ashei) pollen since the mid-1980s. We have shown that the pollen from mountain cedar populations in southern Oklahoma and Texas can be carried on southerly or southwestern winds during the pollen release period in December and January.
Every winter from 1998 to 2015, the Aerobiology Lab provided daily on-line forecasts to warn persons allergic to this pollen of possible exposure risk to mountain cedar pollen. Examples of these forecasts for transport of mountain cedar pollen from populations in Oklahoma and Texas are shown in these links. In each of the the forecast describes the conditions for pollen release at the site and the maps show the path of transport based on HYSPLIT trajectories of predicted air movement. Each of the trajectories show the movement of air masses over 48 hours, and the possible distances the pollen can travel are often remarkable. The London, Ontario, Canada NAB station has registered cedar pollen several times on days when the trajectories showed air mass movement in that direction. One of these events occurred on 15 January 2014 as described in this Plos One journal article.