East Tennessee Weather: First Summer Weekend Brings Heat Wave with a Side of Safety Tips

Okay, my friends, the heat is ON!
On this Friday, June 20, 2025, at 8:31 AM EDT, East Tennessee welcomes the official start of summer with patchy fog, comfortable morning air, and the setup for the season’s hottest weather yet. A heat wave is brewing, bringing sizzling temperatures this weekend and into next week. From the vibrant streets of Knoxville to the misty trails of the Great Smoky Mountains and the rugged charm of the Cumberland Plateau, the EastTNweather platform, led by meteorologist Mike Witcher, delivers hyper-local updates via its app, website, YouTube, Roku, Amazon Fire, and Apple TV to keep you weather-ready. 

Friday: Summer Begins with Fog and A Comfortable Feeling
Happy first day of summer, East Tennessee! Friday starts with patchy dense fog, especially in areas that saw rain yesterday, such as the Cumberland Plateau, the TN/KY border, and Upper East Tennessee near the Tri-Cities. A DENSE FOG ADVISORY is in effect for these regions until 9-10 AM, so drive cautiously in low-visibility areas like Sevierville, Morristown, or along the Tennessee River near Chattanooga. Morning temperatures begin in the 60s, with dew points in the mid to upper 60s, offering a more comfortable feel thanks to drier air settling in post-cold front. By lunchtime, partial sunshine pushes temperatures to the upper 70s, with highs reaching the mid-80s, slightly above the seasonal average of 81°F. The heat index remains manageable, around the upper 80s, with no significant humidity spike today.

Rain chances are minimal, as high pressure begins to build, ensuring a mostly dry and sunny day across East Tennessee. The EastTNweather app is your go-to for tracking fog dissipation and any stray showers, with its Interactive Radar offering past, current, and two-hour future projections. Seize the day for outdoor activities like hiking in Cades Cove, exploring markets in Jonesborough, or strolling Chattanooga’s riverfront. The comfortable air makes it ideal for morning commutes in Knoxville or short hikes in the Smoky Mountains. Check the app for fog alerts and enjoy the pleasant start to summer!

Saturday-Sunday: Our First Heat Wave Takes Hold
The season’s first heat wave arrives this weekend, June 21-22, 2025, as a strong ridge of high pressure builds over East Tennessee. Highs soar to the low to mid-90s both days, with dew points starting in the mid to upper 60s on Saturday, keeping the heat index around 95-100°F. By Sunday, dew points climb to the low 70s, pushing the heat index near or above 105°F, meeting heat advisory criteria across the region, including the Cumberland Plateau and Smoky Mountains. The UV index will be extremely high due to the high summer sun angle, increasing sunburn risks for outdoor activities in Knoxville, Chattanooga, or Pigeon Forge.

Rain chances remain low, with high pressure ensuring mostly sunny and dry conditions. Isolated diurnally driven afternoon storms are possible, especially south of I-40 in Chattanooga, Cleveland, or Athens, but rainfall will be minimal, under 0.25 inches. The EastTNweather app’s long-range forecasts will confirm this scorching weekend, with alerts for potential heat advisories. Plan water-based activities like kayaking on the Tennessee River in Chattanooga, swimming in the Smoky Mountains’ streams, or visiting splash pads in Knoxville, but prioritize heat safety: stay hydrated, apply high-SPF sunscreen, and take shade breaks. Check on neighbors, especially the elderly, in humid areas like Cleveland or Sevierville. North of I-40, including Morristown and the Tri-Cities, may feel slightly less sticky on Saturday, while south of I-40 faces higher humidity by Sunday. The platform’s streaming updates on YouTube, Roku, Amazon Fire, and Apple TV provide heat safety tips, ensuring flexibility for your summer plans.

Next Week: Heat Wave Persists with Afternoon Storms
The heat wave continues into next week, with highs in the low to mid-90s and lows in the 60s to 70s. As high pressure shifts to the Eastern Seaboard, a southerly flow draws moisture from the Atlantic and Gulf, pushing dew points to the low 70s and heat index values to 100-105°F by Monday. This humidity fuels classic summertime afternoon storms starting Tuesday, with daily chances for scattered showers and storms through the week, producing 0.25-0.5 inches per day. These storms are unlikely to be severe but may bring brief heavy rain, particularly south of I-40 in Chattanooga, Cleveland, or Athens. North of I-40, including Knoxville and the Tri-Cities, expects spottier showers.

The EastTNweather app’s extended forecasts will track this heat wave and storm chances, with alerts for heat advisories or localized flood risks. The platform’s streaming updates help plan for the heat, ensuring you stay cool during outdoor events in Athens or Cleveland. The low to mid-90s offer a vibrant summer vibe, with the app’s precision helping you dodge showers for hikes in the Cumberland Plateau or festivals in Knoxville. Stay tuned to the app for updates as the week evolves, keeping your summer plans safe and thriving. With the high UV index, continue applying sunscreen and wearing protective clothing for outdoor activities like lake trips or barbecues.

Rainfall Outlook: Minimal This Weekend, Isolated Storms Late Next Week
Over the next seven days, rainfall totals will be minimal, under 0.5 inches across East Tennessee, thanks to the dominant high pressure this weekend. Isolated afternoon storms may produce light rain south of I-40, particularly in Chattanooga or Cleveland, but significant rainfall is unlikely until next week. Starting Tuesday, daily afternoon storms could bring 1-2 inches over the week, with heavier amounts possible in areas hit by repeated storms. The EastTNweather app’s Interactive Radar and flood alerts will be vital for monitoring next week’s rain, especially in flood-prone areas like Sevierville or Kingston near the Little Pigeon or Clinch Rivers. Check the app daily to stay ahead of potential flooding as humidity rises.