8:27 p.m. EDT July 31, 2015   Freakishly hot, dry weather in the Pacific Northwest is killing millions of fish in the overheated waters of the region's rivers and streams.

“We’ve lost about 1.5 million juvenile fish this year due to drought conditions at our hatcheries,” Ron Warren of Washington State's Department of Fish and Wildlife said in a statement. “This is unlike anything we’ve seen for some time."

Sockeye salmon losses in the Columbia River due to the heat are in the hundreds of thousands, said Jeff Fryer, senior fishery scientist with the river's Inter-Tribal Fish Commission. The fish were returning from the ocean to spawn when the "unprecedented" warm water killed them, he said.

Water temperatures in the Columbia River — part of which runs along the border of Oregon and Washington  — reached the low 70s shortly after July 4, something that doesn't usually happen until August, if at all, Fryer said.

High temperatures — coupled with the low water levels — can be lethal to fish, according to the Oregon Department of Fish and Wildlife. With no end to the drought in sight, there could be additional fish die-offs, said Rod French, a fish biologist with the department.

Dead and distressed sockeye salmon found earlier this month in the Deschutes River in Oregon likely came from the Columbia River and were bound for other locations before they swam into the Deschutes in search of cooler water, the department said. Early pathology results suggest they died from columnaris, a bacterial infection typically associated with high water temperatures and/or low levels of dissolved oxygen.

In Idaho, "it's a tough year for all (migrating) fish, including sockeye," Mike Peterson, Idaho Fish and Game's senior sockeye research biologist, said in a statement.

Recreational fishermen in the region are also feeling the heat: Warm stream temperatures due to low flows and hot weather cause fish trauma, disease, and deaths, which has prompted the closing of streams to all fishing along the Washington Cascades, Richard Heim of the National Oceanic and Atmospheric Administration wrote in this week's U.S. Drought Monitor report.

“When streams get too warm, fish are stressed and as a result the fishing goes downhill fast,” Rick Hargrave, information and education division administrator at the Oregon Department of Fish and Wildlife, said in a statement. “Fish stop biting or retreat to deeper, cooler water where they are harder to catch."

July will likely be one of Seattle's hottest single months on record, the National Weather Service reported.

On Friday, the city hit 90 degrees for the 11th time this summer. That's an all-time record for normally mild Seattle.

The current heat wave is expected to last into early next week. Meanwhile, 100% of Washington and Oregon are now in a drought at the same time, something that hasn't happened since 2001.

The trouble for the fish actually began months ago, when a lack of snowpack from an unusually warm winter resulted in drought conditions throughout much of the Pacific Northwest.

Typically, a decent snowpack slowly provides water to rivers and streams, helping to sustain fish through the drier summer months, according to the Washington Department of Fish and Wildlife. But, with little or no snowpack, flows in many rivers have dropped significantly and water temperatures have increased — deadly conditions for fish.