Expansion of drought conditions across the upper Midwest caused NOAA's Climate Prediction Center to issue an unscheduled update Friday to its U.S. Seasonal Drought Outlook.

Drought conditions that have worsened recently, affecting parts of the northern Plains and the Upper Mississippi Valley, should continue and may expand across eastern Montana, Minnesota, the Dakotas and parts of Iowa, forecasters said in a statement. [Map]

Drought is expected to persist over much of the central and southern Plains and in parts of the Southwest.

Meanwhile, recent heavy rains due to the onset of the U.S. monsoon season should ease drought conditions and reduce wildfires in Colorado and parts of the Southwest, although long-term drought is likely to continue.

Higher-than-normal temperatures, which have exacerbated drought conditions in part of the West and contributed to a busy wildfire season, are expected to persist this summer, NOAA officials said last month.

Natural Disasters: Top 10 U.S. ThreatsGlobal Warming Fuels U.S. Forest FiresScorched West to Sizzle All Summer, NOAA SaysLong History of Southwest Droughts Confirms Looming Water ShortageDeserts Might Grow as Tropics Expand