The least annual precipitation in the western interior of North America occurs in the
northern Great Plains, including an area that encompasses parts of south-eastern Alberta,
south-western Saskatchewan and eastern Montana. During 1999–2001, most climate
stations in this region had record low precipitation. This paper examines this three-year
drought in the context of historical climate records from Medicine Hat, Alberta and
Havre, Montana and summer (June–July) and annual (August–July) precipitation reconstructed from standardized tree-ring widths (residual chronologies) from Pinus contorta
(lodgepole pine) sampled in the Cypress Hills of Alberta and Saskatchewan and the Bears
Paw Mountains of north-central Montana. Drought is operationally defined as precipitation
in the lower 10th and 20th percentiles.
