The month of June has been relatively benign in terms of overall temperatures along the I-95 corridor, but the flip to July on Wednesday will set off the atmospheric furnace in the northeastern states. The time period from tomorrow through Saturday, the 4th of July, will feature afternoon high temperatures near or even slightly above the 100-degree mark in much of the DC-Boston corridor with record highs in jeopardy. Intense upper-level high pressure ridging will be the key player and catalyst for the excessive heat and humidity in the northeastern part of the nation. At the same time, the western states will enjoy colder-than-normal conditions with deep upper-level trough persisting in that part of the nation.
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An overall active weather pattern across the nation will continue into the month of July and it is currently resulting in some severe weather across the central Plains and also the risk of flash flooding. In fact, the risks of severe weather and flash flooding will extend well to the east during the next few days and likely reach the Mid-Atlantic region at the start of the upcoming weekend. Low pressure and a painfully slow-moving frontal system will play key roles in the unsettled weather conditions into the weekend. Looking ahead to next week, hot weather will push into the DC-to-Philly-to-NYC corridor by Tuesday and high temperatures well up in the 90’s are likely in the big cities through the end of the work week.
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The summer season is upon us, and probabilities are quite high that overall temperatures in the Arctic region will be at or below normal if long-term trends hold true. In fact, temperatures in the Arctic region during the first half of June are at historically low levels when compared to any year back to 1958 which is when data records began for this area. Interestingly, water temperatures in portions of the Atlantic Ocean have cooled off quite noticeably during the past year or so and cooler-than-normal water in the Main Development Region of the tropical Atlantic can have an inhibiting effect on tropical activity. Perhaps this change in water temperatures in the Atlantic Ocean and the drastic start to the summer season with respect to temperatures in the Arctic is signaling an upcoming change in the Atlantic Multidecadal Oscillation (AMO) which has been in a “positive” phase since the middle 1990’s.
“Normal” temperatures in the Arctic region during the summer season are right around the 32 degree (F) freezing mark and as long as temperatures average at or below normal, additional melting of Arctic sea ice will have its limitations. Meanwhile, the other nine months of the year in the Arctic region have consistently featured above normal temperatures in recent years. One possible explanation of this persistent temperature pattern in the Arctic region featuring nearly normal to below-normal summertime conditions and warmer-than-normal weather during the coldest nine months of the year is increased levels of water vapor in the atmosphere.
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Sometimes during the month of June, the jet stream retreats safely to the north into Canada, and the weather settles down across the continental US...that certainly does not appear to the case this year. Upper-level troughs of low pressure and colder-than-normal air masses continue to drop into the US from Canada, and this is resulting in severe weather outbreaks and there will be an enhanced threat during the next few days. Next week promises to feature another impressive upper-level trough by June standards that will no doubt be impactful with more severe weather threats and widespread cooler-than-normal conditions.
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El Nino is on the way, and it looks like it will be a strong event...
The equatorial Pacific Ocean is transitioning into El Nino conditions (i.e., warmer-than-normal sea surface temperatures) and signs point to a strong event by the summer and fall seasons with big implications on tropical activity in the Atlantic Basin. Looking ahead, it appears this El Nino event may even last into the upcoming winter season of 2026-2027 which no doubt would have some implications across the continental US.
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Much of the week ahead will be rather cool and unsettled across the northeastern part of the nation with a persistent upper-level trough of low pressure sitting nearby. This upper air pattern will keep temperatures generally suppressed to below-normal levels in the Great Lakes, Mid-Atlantic and Northeast US and there will be a shower threat from time-to-time. By the weekend, important changes will take place as the upper-level trough over the northeastern US retreats off to the northeast and an upper-level ridge of high pressure edges its way into the area from the western states. This ridge will intensify early next week, and the result could be 90+ degrees in the Sunday/Monday/Tuesday time period in places along the I-95 corridor. Looking beyond, it appears that the big-time warm up early next week will not last too much longer as a frontal system next mid-week is likely to return temperatures to more seasonal levels.
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As noted in the 2026 Tropical Outlook, El Nino is going to be a major player with respect to the upcoming tropical season in the Atlantic Basin and signs are increasingly pointing to one of the strongest episodes in the last 50 years. The most powerful El Nino events in recent history took place in 1982-1983, 1997-1998, and during 2015-2016, and this upcoming occurrence could rival all of them in terms of its magnitude. Not only have surface water temperatures climbed dramatically in recent days across the tropical Pacific Ocean, but some very warm water relative-to-normal lurks just beneath the surface…and it is “bubbling” up to the top. El Nino will have worldwide impacts during the summer and fall seasons and likely be a big inhibiting factor to the Atlantic Basin tropical season due to increased subsidence and wind shear (hostile conditions for tropical systems). Should El Nino continue into the first part of 2027 - and odds are quite good from this vantage point - it could have big implications on the winter season across the continental US...something we’ll monitor in the months to come.
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May gets underway on Friday, and it looks like a cooler-than-normal pattern will dominate in the eastern half of the nation to at least the middle of the new month. Multiple cooler than normal air masses are likely to push into the north-central states from central Canada during those next couple of weeks and these will ultimately spread to the south and east and encompass the Great Lakes, Mid-Atlantic, and Northeast US. A favorable pattern for the transport of cooler-than-normal air masses from Canada into the US will feature a persistent upper-level trough centered near the Great Lakes as well as some “high-latitude blocking” up across northeastern Canada and Greenland. In addition to the expected cooler conditions, multiple rain events are on the table during the next couple of weeks beginning with one from later today into early Thursday which will impact the Mid-Atlantic region.
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A combination of ingredients will come together later today and tonight to enhance the risk of severe weather in the Middle Mississippi Valley region with a focus on the region from Arkansas to Indiana. One of the contributing factors in today’s severe weather threat is an active jet stream that has intensified in recent days across the central and southern US in an atmospheric response to the initial phase of El Nino in the tropical Pacific. The threat of severe weather will shift slightly to the south and east on Tuesday mainly to the Middle and Lower Mississippi Valley regions. In fact, the threat of severe weather will likely continue well into the month of May as additional cold air masses are destined to drop southeastward from central Canada into the northern US. This evolving weather pattern will produce below-normal temperatures across much of the eastern half of the nation from late April into at least the middle of May and multiple rain events are likely to be included from the Rockies to the eastern seaboard.
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As noted in the 2026 Tropical Outlook, El Nino is likely to be a major player with respect to the upcoming tropical season in the Atlantic Basin and all signs continue to point to the increase of water temperatures in the equatorial Pacific Ocean. Not only have surface water temperatures climbed dramatically in the tropical Pacific Ocean in recent days, but some very warm water lurks just beneath the surface, and it is “bubbling” up to the top.
The development of El Nino in the tropical Pacific is actually having some current effects on the upper air flow across the continental US with a more favorable environment for severe weather outbreaks and better opportunities for rain from the Rocky Mountain States to the Mid-Atlantic region. Looking ahead, the combination of an El Nino episode in the Pacific Ocean and an area of cooler-than-normal water in the Atlantic’s Main Development Region may result in below-normal tropical activity in the Atlantic Basin during the summer and fall seasons. Should El Nino continue into the 2026-2027 winter season - and odds are good - it would also have big implications for the weather across the continental US...something we’ll monitor in the months to come.
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