The remains of Tropical Storm Barry will get picked up by a mid-latitude trough, which will move across New England on Thursday. As teams set up at the track that day, there will likely be showers and thunderstorms in the area, especially in the first half of the day.
By the time on-track action starts on Friday, the trough will be well to the east and high pressure will be building over the area. This large high pressure ridge will dominate the eastern U.S. over the weekend, and bring above normal temperatures to much of the country.
At Lime Rock Park, high temperatures on Saturday and Sunday are expected to easily reach into the lower 90s. With dewpoint temperatures near 70, it will feel humid as well, with a heat index pushing 100 degrees. Anyone going to the race will need to be prepared to stay hydrated - drink plenty of water and find shade whenever possible to avoid heat exhaustion.