The heat is suffocating.  Here are 10 maps that tell the story.

1. D.C. – the nation’s heat epicenter


At 2 p.m., Washington, D.C. had the second highest heat index in the nation of 98 (using The Weather Channel’s map, tied with several other locations). Recall, the heat index takes into account both the air temperature and humidity to provide a sense for what the air feels like.

Related: The origins of the heat index and why it’s important

2. The I-95 corridor bakes!


At 2 p.m., D.C., Philadelphia, and New York were the three hottest cities east of the Rockies, with temperatures of 93-94 degrees.

3. Heat hasn’t yet reached today’s peak


The HRRR, a high resolution forecast model, says today’s high temperature should max out around 98-99 degrees in D.C. (I think we’ll probably be more in the 96-98 range).

4. Dew points are oppressive

(Unisys Weather)

Dew points, the temperature the air would have to fall to in order for dew to form (i.e. the temperature at which condensation will occur), are uncomfortably high.  Anything around 70 or higher is gross.  D.C.’s dew points have varied between 68 and 72 today.

5. We’re getting cooked

GFS model simulation of today’s heat dome and atmospheric heights at the 500 mb pressure level. (

The intensity of the high pressure system over our region is at record high levels.  For more details, see our earlier post: Pressure cooker! Washington, D.C. matches record high pressure reading in heat wave

6. Modest relief at night


The overnight hours don’t cool off dramatically. Shown above are Wednesday morning’s forecast low temperatures from the high resolution NAM model.  Lows won’t drop below the upper 70s to near 80 in the city. Bad, potentially dangerous news if you don’t have air conditioning. Be sure to stay hydrated and take a cool shower if you feel overheated.

7. Hot again tomorrow


The latest NAM model shows afternoon high temperatures Wednesday again in the upper 90s in the D.C. area

8. Thursday and Friday: little relief


Highs are forecast to be in the mid-90s according to GFS model simulations (shown above) and the humidity will be just as bad (maybe worse).

9. But…last year was much worse

High temperatures on June 29, 2012 – the day of the derecho. This was the 2nd day of heat wave that featured 11 straight days above 95 (

Swelter in Place! We had weather as hot or hotter than today on 11 straight days, including 5 days in the triple digits.  The average high during the June 28-July 8 stretch was an incredible 99.5!

Link: Historic heat wave in hindsight: Hottest on record in Washington D.C., hotter than 1930

10. Let’s not even talk about 2011

Note: these were the heat indices at 10 a.m. (on 7/22/2011)! Look who had the highest reading. (

Sweat Ceiling! On July 22, 2011, the heat index reached an inferno-like 121 in D.C.  We really shouldn’t be complaining about today’s 100-105 levels.  The map above shows the heat index was already 108 at 10 a.m.!

What’s this? Below normal temperatures? (One not so red hot map)


By Monday morning, the GFS model simulates temperatures in the D.C. area 8-10 degrees below average. That means 60s for lows and low 80s for highs (assuming the cold front clears, fingers crossed).