June 29, 2026 Monday Mega Heat Dome
Forecasts trending hotter across the Big Cities of the Eastern Seaboard with 100°F+ likely for 71 million Americans into 4th of July weekend
June 2026 was the 18th-warmest June in the 132-year national record (1895–2026), at 70.6°F against a 1991–2020 normal of 69.5°F (+1.2°F).
June 2026 was the 32nd-wettest June in the 132-year national record (1895–2026), at 3.3in against a 1991–2020 normal of 3.1in (+0.2in).
NOAA/NCEI Climate at a Glance, contiguous United States. This is the observed record for the month, not a score of anything said in this piece — the forecast ledger begins 2026-08-17 and cannot reach earlier posts.
The main weather story this week continues to be the “Mega Heat Dome” forming across the Eastern United States.
High Temperatures next 8-days — watching the population of at least 90°F + 100°F skyrocketing as the large population centers of the East Coast see extreme heat wave for multiple days.
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Upper-Level Height Anomaly | AIFS-Single Next 10-days
While very strong troughing digs into the Pacific Northwest = much cooler air across the West, a major ridge forms over NE Arctic Canada and extends down an axis into the U.S. Southeast forming the heat dome.
Ridging builds across the Eastern U.S. —> dry and hot —> HEAT DOME
Into Summer —> Height Anomalies don’t tell entire story … actual height does!
5940 m height contours — not quite record level near 6000 m but plenty of subsidence to ensure very hot surface temperatures. We’re entering the “dog days of summer” when the weather pattern stagnates with long-lasting, slow moving ridges.
NWS Precipitation Next 72-hours —> Thursday Afternoon
Nice to see South Florida with heavy rain from the easterly flow around the bottom periphery of the “heat dome”
My favorite parameter — next 48-hours of HRRR Precipitable Water
Weather Into Tuesday Morning
HRRR radar next 18-hours through Tuesday Noon ET
HRRR Next 48-hours simulated Radar through Wednesday 2 PM ET
Weather on Tuesday
Blend of Models —> Precipitation Next 7-days
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Flagship model: ECMWF AIFS 18z —> Integrated Vapor Transport next 10-days
Heat dome shuts down the Gulf of Mexico. Looks like a much drier than normal period ahead for the next 10-14 days to start July.
Germany ICON 18z | Precipitable Water | My Favorite Parameter
Tropical system off the Southeast coast has a nice blob of 2”+ PWAT and maybe become a nice tropical depression or storm for Georgia / North Florida / South Carolina = rainfall and clouds to break the “heat dome”
Temperature Analysis | RTMA | 7:45 PM ET
About 78 million population at least 90°F at 7:45 PM ET
Temperature Anomaly | RTMA | 7:45 PM ET
Lower 48 was -1.3°F below normal with chilly temperatures (relative to last days of June) across the Pacific Northwest and Northern Rockies
Heat Index Temperature | RTMA | 7:45 PM ET
100s into the Great Lakes
High Temperatures Next 9-Days —> Wednesday July 8th
Northeast Regional Zoom
Washington D.C. hottest on Friday with 105°F (very hot)
NYC Central Park at 102°F on Thursday and Friday, and 100°F on Saturday, July 4th
Boston to 100°F on Thursday
Low Temperatures on Tuesday
Muggy with lows in the mid-70s into Great Lakes
High Temperatures on Tuesday
233 Million at least 90°F
ECMWF Flagship Ensemble Mean Temperature Anomaly next 15-days
Trough —> cooler across the Pacific Northwest with huge negative anomalies of -20°F vs. the formation of a ridge / heat dome across the Great Lakes and into the Mid-Atlantic + Canada
Week 1 —> June 29 to July 5
Week 2 —> July 6 to July 12
Tropical Update: Atlantic Basin — (15-day tracks forecast from EPS 12z)
This disturbance (10%) is not being picked up by my storm tracker, but the minimum sea level pressure might be too high against the background environment of Bermuda High
Western Pacific lights up with 2+ Typhoons likely with long-tracks = huge ACE
Next names are Bavi & Maysak
Invest 95W will become a MONSTER. I would not be surprised to see Category 5 — 155 knots (T 7.5) or higher
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My Atlantic Hurricane Season Forecast (2026)
From April 7, 2026: Atlantic Seasonal Hurricane Forecast: (11/5/2)
9-13 Named Storms (11 most likely)
4-7 Hurricanes (5 or 6 most likely)
1-3 Major Hurricanes (2 most likely)
Accumulated Cyclone Energy: 75-85 (well below normal)
NOAA 2026 Atlantic Hurricane Season Forecast
- Milepost
- 970 · laid 2026-06-30T01:36:46.057000Z
- Source
- https://weather.substack.com/p/june-29-2026-monday-mega-heat-dome
- Digest
- d0eae62446982224296e5c0faae28f82be6600484d599137c8335c7efc090ebf
- Machine
- JSON