The Pacific Northwest is again experiencing surging spring heat that shattered temperatures this past week and prompted red-flag warnings for fire risks in lowland portions of Southwest Washington.

Last year, intense May warmth brought a sudden melt of a big mountain snowpack, causing flooding in north central and northeast Washington as the Okanogan River reached its highest flood stage in four decades.

This year, the statewide snowpack, as of Friday, averaged only 58 percent of the median amount for that date. So instead of being concerned about high water, state officials are preparing for summer drought, which can raise the potential for wildfires, reduce irrigation flows to farmers and make life difficult for salmon that depend on cool water to survive.

“When you look at some of the snowpacks in some of the basins, it looks like they are doing a swan dive off a cliff,” said Jeff Marti, a state Ecology Department official who noted that Gov. Jay Inslee already has issued drought-emergency declarations in the Okanogan, Methow and upper Yakima watersheds, because low snowpacks are expected to crimp water supplies.

For Seattle-area residents who endured a snow-laden February, it may seem odd to be talking about drought. But many of the winter storms that hit the Puget Sound region, as well as the Yakima basin, did not bring heavy accumulations in the upper reaches of Cascade drainages that act like a kind of natural reservoir.

In a long cool spring, snow slowly melts to feed the region’s streams and rivers. But the last week has been like the middle of summer: Friday’s high of 86 degrees at Seattle-Tacoma International Airport broke the record of 80 degrees set in 1993, according to the National Weather Service.

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As snow retreats, the ground underneath quickly dries out. Small fuels (branches and other wood up to 3 inches in diameter) already have a low moisture content in lowland areas, and are primed to burn, according to John Saltenberger, fire weather program manager at the Northwest Interagency Coordination Center.

Already, as of May 6, there have been reports in Washington of 239 outdoor fires, ranging from false alarms to smoldering campfires to woodland blazes, and that’s the highest number in the past decade, according to Janet Pearce of the Department of Natural Resources. These fires collectively burned 570 acres.

To prepare for summer, state officials are urging west-side — as well as east-side — homeowners to remove low-lying limbs (up to 10 feet off the ground) from trees near their homes.

The outlook for the summer months is for an above-average risk for larger fires in the Pacific Northwest. This increased risk extends to British Columbia, where huge fires that raged last year sent smoke into the Puget Sound region and other parts of Washington.

“British Columbia is anticipating a busy fire season this summer,” Saltenberger said.

Farmers on edge 

The hot weather is putting farmers on edge in the Yakima Valley, one of the state’s most bountiful farming areas with crops that include apples, pears, cherries, wine grapes and hops.

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Many Yakima farmers hold junior water rights. That means they will get reduced amounts in times of shortages. In an early May forecast, the Bureau of Reclamation predicted junior water-rights holders would get about 25 percent less water than in a year with a bountiful snowpack. That forecast will be revised in June, and the amount of water could fall significantly if warm, dry weather continues through May.

“There will be restrictions,” said Scott Revell, manager of the Roza Irrigation District, which operates a canal and smaller laterals that deliver water to junior water-rights holders in the heart of the Yakima farm belt.

Revell said the district’s priority is to keep irrigation water flowing at least until mid-September, and hopefully until the end of October. That would prove much more difficult if a warm May causes the Bureau of Reclamation to cut back junior water-rights holders by another 10 to 15 percent, he said.

Inslee’s drought declarations make it easier for farmers to use alternative sources of water such as wells, and expedite the process for temporarily transferring water rights from one user to another.

Challenges for salmon

May also is a critical season for salmon, with young fish spawned in the wild or reared in hatcheries starting to make their way to ocean feeding grounds.

 Strong, cool flows of water help push the fish downstream. With a lighter snowpack, there is less of that water in some drainages. Less water can mean slower flows and warmer temperatures, which can reduce survival rates of young salmon that may be more vulnerable to predators.

“We don’t have as much water as we thought we might have. It could get pretty dicey when they reach the Lower Yakima,” said Bill Bosch, data manager with the Yakama Nation Fisheries. “When you don’t have a lot of water, it spreads out and gets real slow. It doesn’t look real good.”

Tribal, state and federal fishery biologists are closely tracking the returns of adult salmon from ocean feeding grounds and how well they are making their way upstream through the Columbia River to reach spawning areas.

Biologists say that warm ocean water in years past reduced the survival rate of the spring chinook that are returning this year. As of May 9,  only 30,118 spring chinook had made their way past Bonneville Dam. The run is expected to fall short of the already low forecast 99,300 spring chinook, which was only half of the average number that have returned during the past decade.

What about climate change? 

When early May feels like August for a second year in a row, it is easy to wonder whether global warming has somehow redefined the Pacific Northwest seasons. But scientists say that short-term weather phenomena, such as record high daily temperatures, or even a record high for an entire month, cannot be closely linked to climate change that scientists say is driven by fossil fuel emissions that are forecast to warm the planet through this century.

But longer term analysis can reveal some trends.

Marti, of the state Ecology Department, said that since 2000, only six times in the month of May have temperatures on average been cooler for that month than the 20th century average.

Karin Bumbaco, the assistant state climatologist, notes that last year, May was more than 5 degrees Fahrenheit warmer than the average temperature for Seattle and Washington state between 1981 and 2010.

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But as early as 2040, or possibly as late as 2069, such May temperatures are expected to be normal, according to an analysis of climate-change models.