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(CNN) -
Drought conditions have expanded and worsened in the western United States, especially the Pacific Northwest, due to last week's record heat wave, according to the latest US Drought Monitor.
"The unprecedented heat in the Northwest, combined with another week of dry weather, led to a worsening of drought conditions throughout the region," the summary of this week's drought figures said Thursday morning.
Temperatures, which ranged between 1 and 6 degrees Celsius above average, increased evaporation, "further drying out soils and vegetation", exacerbating the drought in the region.
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Many areas in the Northwest saw drought classifications worsened by category, with expansions of "severe" and "extreme" drought areas.
The Southwest was unchanged except for some expansion of "extreme" drought in central Arizona.
Currently, drought coverage in the West has risen to an all-time high of 93%, with almost 60% in 'extreme' or 'exceptional' (the two highest categories).
There are five completely dry states;
California, Oregon, Nevada, Utah, and North Dakota.
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Heat wave and unprecedented temperatures in the United States
A historic heat wave is weighing down much of the Pacific Northwest in the United States, making the drought even worse.
And July is just beginning.
Portland set an all-time high temperature record for three days in a row.
Seattle also beat its own record, set on Sunday.
Across the border, Lytton in British Columbia also broke all-time records on Sunday and Monday, recording temperatures that were nearly 9 degrees Celsius above normal.
Kristina Dahl, a climate scientist at the Union of Concerned Scientists, says the heat wave is "unprecedented."
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"We saw heat records over the weekend and we beat them again the next day," Dahl told CNN, "especially in a part of the country where this kind of heat doesn't happen very often."
At the opposite end of the country, more than 40 million people in the Northeast are also under heat warnings, including the New York, Philadelphia and Boston metropolitan areas.
Although the heat will not be as strong as in Oregon and Washington state, records for the date could be set in the Northeast before temperatures cool down on Thursday.
Extreme heat is one of the deadliest consequences of climate change, killing more people than any other weather-related event.
Drought
