(Wine-Searcher) - California isn't the only place where grapegrowers are looking anxiously at the skies.

Oregon and Washington are experiencing their hottest summer on record so far, just one year after their previous hottest summer.

Last year it was good news: both states also celebrated their largest wine harvests ever. But it's also unusually dry, and Oregon grapegrowers are beginning to get nervous Temperatures in normally cool, wet Willamette Valley have reached as high as 99ºF (37ºC).

Moreover, while the drought in Oregon has not been as long or as severe as in California, "the vast majority of vineyards in Willamette Valley are not irrigated", says climatologist Greg Jones of Southern Oregon University.

"I just got back from a growers' meeting," Jones told Wine Searcher. "The conversation was all about conserving soil moisture. If you're not doing much irrigation, a year like this is a real challenge. But if you are dependent on irrigation, people today were worried about when they are going to get cut off from water."

In Washington the situation is not as disturbing, yet, because Eastern Washington is generally hot and dry anyway, so growers are better prepared. Moreover, Washington vineyards are mostly planted with warm-weather grapes like Cabernet Sauvignon and Merlot, whereas Oregon has hung its reputation on cool-climate Pinot Noir.

But Jones said farmers of all crops in Washington, including wine grapes, are beginning to keep an eye on the water levels of the Columbia and Snake Rivers.

"The whole area is driven by access to that water," Jones said. "If they had a downturn in the amount of water, they could have a real problem."

In wetter Oregon, paradoxically, the dryness problem is more immediate.

The NOAA (National Oceanic and Atmospheric Administration) is predicting more hot, dry weather for the Pacific Northwest – and California as well – over the next 30 days. But it's the weather; anything can happen.

However, while California might get help from what appears to be a forming El Niño effect, "El Niño hasn't historically brought very much rain to the Pacific Northwest", Jones said. "It tends to bring rain from Northern California south. I'm very hopeful that northern California southward will have a cooler, wetter winter. I'm not as hopeful about the Pacific Northwest."

Of course, it's only the second week of July, and even an early harvest is still several weeks away.

"The last two weeks are really what will define the vintage," said Oregon Wine Board communications manager Michelle Kaufmann.