Warmth and dryness will build in the western United States during the summer of 2015, worsening the historical drought conditions that have plagued California for four straight years, while the Gulf Coast will experience an abundance of moisture, raising concerns for flooding at times, AccuWeather Inc. predicts.

In the nation's midsection, severe weather is expected to continue into summer, with the overall tornado count increasing from last year. In the Northeast and mid-Atlantic, above-normal temperatures will mark a noticeable difference from the cooler-than-average summer of 2014.

More 90-Degree Days Than Last Year Forecast for Northeast, Mid-Atlantic

Warmth from central Canada and the northern Plains will flow into the Northeast this summer, leading to above-normal temperatures and drier conditions for much of the region.

"I'm not expecting extreme heat, but periods of warmer-than-normal temperatures will come and go during the course of the summer," AccuWeather.com Expert Long-Range Forecaster Paul Pastelok said.

After a cooler-than-normal summer of 2014, the East is expected to be hit by more 90-plus-degree days this summer. In Philadelphia and New York City, there may be as many as 10 more than last summer.

For much of the summer, the central and southern mid-Atlantic will experience showers and thunderstorms, with Washington, D.C.; Baltimore; and Philadelphia in the line of fire.

Wet, Buggy Season Ahead for Southeast, Central Gulf Coast, Tennessee Valley

From the Southeast to the Gulf Coast and Tennessee Valley, the summer of 2015 will bring very wet conditions as a result of warm water temperatures in the northern Gulf and a building El Nino. Flash flooding could be a concern at times.

"I would consider stocking up on the bug spray this year down across the Tennessee Valley and the Gulf Coast because it looks very wet," Pastelok said.

Extreme heat should be kept at bay, but high humidity and muggy conditions will plague the region.

As for tropical activity, the northern Gulf states could be affected as early as June.

"Water temperatures are running much warmer than last year," Pastelok said. "It may not take much to spawn a weak tropical system to enhance the rainfall on the Gulf Coast this year."

Rainy Weather in Store for Southern Plains, Lower to Mid-Mississippi Valley

Rainy weather will spread across parts of Texas for much of the summer, focusing on the lower Rio Grande Valley and southwestern portion of the state.

Through early June, showers and storms will improve the drought conditions across northern and northwestern Texas, but the region could dry out again as rain will fall mainly west of those areas during midsummer.

As the monsoon picks up, storms will drench the Four Corners region, delivering above-normal moisture.

Overall, the southern Plains and lower to mid-Mississippi Valley will see fewer 90- and 100-degree days than in recent years.

"It's not as dry going into this summer season across the entire southern Plains, and I think that will have an impact on how high and how consistently we'll hit above 90 this year," Pastelok said.

Severe Risk to Continue for Midwest, Northern and Central Plains

The northern and central Plains and much of the Midwest will face conditions drier and warmer than those of last summer.

"Drier-than-normal conditions in the winter and for the most part this spring will lead to … hotter temperatures," Pastelok said.

Southeastern Iowa, Missouri, Illinois, eastern Kansas, and Oklahoma may have a shot at dodging this extreme heat with more possibilities for rain.

Spotty areas of thunderstorms, some of which can be severe, may break out in June, increasing the potential for tornadoes.

The middle of the summer will feel hot across the Dakotas, Nebraska, Iowa, and Minnesota.

"They will be dry, and the heat will just build as we go into the summer months, especially June and July," Pastelok said.

Severe Drought to Worsen in California, Expand Northward at Full Force

The drought in California will continue to worsen this summer, after the heart of the winter season brought little snowfall to the Sierra.

Without rain in the forecast, there are indications fire season, which typically occurs from June through October, could be one for the record books.

"The wildfire season has already kicked off a little early," Pastelok said. "I think the frequency will really pick up later in the summer and early fall."

Drought conditions are forecast to expand northward at full force into the Pacific Northwest, especially east of the Cascades.

"It looks to me like they'll continue to get drier and drier, and by June and July, it'll have reflection on temperatures as well," Pastelok said. "It should get hotter across those areas."