Temperatures so far this June have been above average overall across the nation, especially in the Central US — for a second month in a row. Through June 20th, it is estimated that the US has been experiencing a temperature of 2.58°F above average, translating to an actual temperature of 70.5°F. The weather can always change in a short amount of time, so the question is whether it will feel like summer during the week of the Fourth of July, one of the most popular holidays in the summertime.
The short answer is that it will feel likely summer across most of the nation, but we want to focus on the East because that is where temperatures may become significantly above average for several days. According to the Climate Prediction Center, there is up to an 80% chance for above normal temperature across the Midwest and Northeast while there is a moderate risk anywhere outside from the northwestern US.
Weather around the world is all connected. Whenever we forecast in the mid to long-range time period, it is important to observe how the weather pattern will evolve not only across the US but on the other side of the Northern Hemisphere. In eastern Asia, a large, upper-level ridge of high pressure, which typically allows for warmer than normal temperatures, will likely develop by early-July. This immediately tells us and other forecasters that a warmup will likely occur across the Central and Eastern US because of this. This ridging over Eastern Asia is historically correlated with ridging over this part of the US.
There is another component that will be one of the big drivers to this upcoming warmup. That is the MJO, or Madden-Jullian Oscillation. This area of enhanced convection cycles around Earth near the equator and can actually have an indirect effect on the weather globally — all because of these thunderstorms and above average rainfall. The below MJO forecast from the European model indicates the MJO transitioning into phase 2, which often brings heat to the East.
With all of that said, a hot first week of July — and possible beyond — is likely overall as a dominate upper-level ridge builds over the Eastern US and sits overhead for multiple days. Based on early-model guidance, the effects of this ridge will begin to be felt around mid-next week as high temperatures into the 90s and 100s become widespread across much of the Central US. Then by the Fourth of July, that heat will likely travel up the East Coast. High temperatures will likely soar into the 90s across the I-95 corridor with isolated high temperatures into the 100s. Some cities may witness their first heat wave of the year, which is when there are at least three consecutive days of high temperatures at or greater than 90 degrees.
This warmth will be quite fitting for July, which is the hottest month for the country as a whole. Along with the warmth will be the risk for rain and thunderstorms. Unfortunately, the Central US should remain wetter than normal while parts of the East Coast will experience rainfall close to average.