The eastern half of the nation is about to get a full taste of summer two weeks ahead of meteorological summer, which begins on June 1, and six weeks ahead of astronomical summer that will officially arrive June 20. AccuWeather meteorologists are forecasting temperatures to surge well into the 80s F over much of the region later this week and into this weekend -- and a few locations may experience their first 90-degree temperature of the season so far. Although temperatures have come close in many areas of the East, there have only been a couple of 90-degree readings near the Gulf and along portions of the southern Atlantic coast. For example, a few locations in southeastern Virginia hit 90 on May 4. In Washington, D.C., and Philadelphia, which have not yet hit 90 this year, the last time temperatures climbed into the upper 80s was on April 28. On the same day in April, New York City hit 85, which was its highest temperature so far this year. The Big Apple is forecast to peak in the middle 80s later this week, but temperatures could flirt with 90 farther south along I-95. Even Atlanta hasn't hit the 90-degree benchmark yet this season. The closest the city came so far in 2021 was 86 F on April 13. The nation's capital has climbed closer to the mark, with an 88-degree reading on April 28. It is getting to be that time of the year for some summery conditions and 90-degree temperatures, AccuWeather forecasters say. "The average first 90-degree day is May 22 in Charlotte, North Carolina; May 24 in Philadelphia and May 31 in Atlanta," AccuWeather Meteorologist Matt Benz stated. The average first dates for 90-degree temperature readings are based on data over the 30-year period from 1991 to 2020. The National Oceanic and Atmospheric Administration's (NOAA) and National Climatic Data Center (NCDC) recently reviewed and updated "normal" temperature and climate variables for the U.S. -- a process that's done every 10 years. "These locations and others will make a run at 90 late this week and this weekend, while widespread highs in the 80s are foreseen even where the temperature may stop just short of 90 from parts of Vermont, New Hampshire, upstate New York and Michigan to northern Georgia, upstate South Carolina, western North Carolina and Tennessee," Benz explained. However, average temperatures during the middle to the latter part of May range from the middle 60s in northern New England and the central Great Lakes to the lower 80s in the Interstate 20 corridor of the Southeast states. Temperatures will begin to trend above average during the first part of this week and will end up close to July-like levels by the end of the week and over the weekend. Even in northern Maine, temperatures could make a run at 80. There will be some cooler spots adjacent to the Atlantic Ocean, its bays and right along the shores of the Great Lakes. Temperatures where a breeze blows off the water can be 10-20 degrees lower than farther inland or where the wind manages to blow toward the water, rather than toward land. Due to an onshore breeze from the Atlantic, highs in Boston most days are forecast to be in the 70s this week and this weekend. Memorial Day may be fast approaching and many may contemplate partaking in summertime activities, especially amid the warmup, but the water temperature is still dangerously low for safe bathing this early in the season in the Midwest and East. Atlantic Ocean water temperatures range from the upper 40s along the Maine coast to near 60 in southeastern Virginia as of Monday and may only rise a few degrees by week's end. At this level there is a high risk of muscle cramps and cold water shock. "Humidity levels will remain rather low much of the week but will begin to climb especially in parts of the Midwest and mid-Atlantic regions this weekend," Benz said. As the temperature and humidity levels climb, so too will the AccuWeather RealFeel® Temperature. In some cases the RealFeel Temperature can surge to 10 degrees or more above the actual temperature during the day considering the strengthening sun during the second half of May -- with the summer solstice less than six weeks away. On Sunday, June 20, the sun's direct rays will be at their farthest north point of the entire year. An upward trend in humidity levels will also occur in the Southeast later this week, but it is not likely to be so noticeable. "For millions in the Southeast who are more accustomed to very warm conditions, this will be a delightful weather pattern without high humidity," Benz said. The same weather pattern that will promote the warm conditions will also keep many areas in the eastern U.S. dry. A northward bulge in the jet stream is forecast to develop over the Central states and build eastward as the week progresses. As this happens, warm air will build in the middle layer of the atmosphere and allow temperatures to trend upward near the ground. Near the core of the warmth, shower and thunderstorm activity will generally be limited and sunshine will be abundant. These conditions are anticipated from the eastern part of the Ohio Valley to much of the mid-Atlantic and Southeast states as the week progresses. On the periphery of a northward bulge in the jet stream, showers and thunderstorms often occur. In this case, wet weather will be most widespread over the South Central states, where storms can be so repetitive that flooding will occur much of this week. Spotty showers and thunderstorms are expected to develop across parts of the Great Lakes to New England this week. From this weekend to early next week, the northward bulge in the jet stream is forecast to shift westward. "This westward shift is likely to allow cooler air to push southward in the Northeast this weekend," Benz said. Showers and thunderstorms would likely accompany that cooling trend from north to south. "Cooler air may reach parts of the Southeast early next week, but that is not set in stone," Benz added. Humidity levels are forecast to be higher next week compared to this week over much of the Southeast. Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.