[citation needed] A North American High moves eastward across the continent,[1] often in the company of one or more low-pressure cells or cyclones.
The cold, dense air does not extend usually above 3 km (1.9 mi) and is lower than the Canadian Rockies mountain range.
The North American High's distance from the warm Pacific Ocean as well as its protection from the Rockies to its West reinforces its intensity.
The average January sea level pressure at its centre is approximately 1,020 millibars (30.12 inches of mercury).
[2] During summer, the Canadian high circulates cool, dry air to the United States located east of the Rockies and parts of southern Canada.