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Posted at 5:00 AM ET, 07/24/2010

Forecast: Hottest day in hottest summer

By Jason Samenow

* Excessive Heat Warning I95, Heat Advisory N&W 12 p.m.-10 p.m. *
* It's so hot (news story) | Post Local coverage | Heat Tips | UnitedCast *
* Outside now? Radar & more: Weather Wall | Tropical Tracking *
* Consec days 90+: 10; Total 90+: 40 (Apr: 2; May: 3; Jun: 18; Jul: 17) *

Today's Daily Digit
A somewhat subjective rating of the
day's weather, on a scale of 0 to 10.


The heat is disgusting, but it cannot get much worse.
Get the 'Digit' on Twitter


Today: Extreme heat and humidity. 99-104. | Tonight: Remaining uncomfortably warm. 76-83. | Tomorrow: Still hot & humid; chance of p.m. storms. 95-99. | A Look Ahead | Get Express Forecast by E-mail


More than two thirds of the way through July, the year 2010 is warmer than any prior year this deep into the summer (defining it as June-July-August) on record. And today could be the hottest day. It may not be the hottest in an absolute sense - as July 6 and 7 hit 102. But when you factor in the humidity -- which will be much higher than those scorching days earlier in the month -- it will feel like a stifling 105-110 degrees. No other day has been that oppressively hot. Sunday, regrettably, remains steamy but some modest relief arrives for early next week.

Temperatures: Latest D.C. area temperature map powered by iMapWeather (base map by Google). Click and hold on map to pan. Double-click to zoom. Refresh page to update. See larger map on our Weather Wall.

Today (Saturday): I was once told by a forecasting professor, "If you're going to predict a record, you better be damn sure it's going to happen." Suffice to say, I'm damn sure we're going to sail past today's surprisingly low record high of 96. In fact, we'll probably be at or above 96 from before noon to past 7 p.m. Under mostly sunny but hazy skies, highs should top out in the low 100s but the heat index may reach 108 or 109 in the mid-to-late afternoon hours. That's dangerous heat and strenuous activities should be avoided under those conditions. A light wind from the west at 6-10 mph won't provide much relief. Confidence: Medium-High

Tonight: It's not going to cool down appreciably. With partly cloudy skies, urban areas only escape the 90s by around 11 p.m. ultimately bottoming out in the low 80s by dawn. The record high minimum of 79 at Reagan National is likely to be shattered. Even the cooler suburbs won't fall below the mid-70s. Confidence: Medium-High

Keep reading for the forecast into early next week...

Tomorrow (Sunday): The heat remains on Sunday, but due to afternoon clouds, we'll probably see fewer triple digit readings but plenty of upper 90s. I still expect heat advisory criteria conditions -- meaning heat indices to 105 with unrelenting humidity. An approaching cold front does bring the chance (30-40%) of late afternoon and evening thunderstorms, a few of which could be intense. Confidence: Medium-High

Tomorrow Night: Thunderstorm activity may linger through the mid-evening, especially south and east of town. Otherwise, skies will gradually clear, and as winds starting coming around from the north and northwest, it will cool off a bit. But it won't be refreshing with lows ranging from near 70 in the cooler suburbs to the mid-to-upper 70s downtown. Confidence: Medium-High


Monday and Tuesday do provide some relief. Humidity levels drop noticeably Monday, but with ample sunshine, the mercury is able to climb back close to 90. While I don't see it as an opportunity to shutoff the A/C, Monday night will be relatively refreshing, with lows in the mid-60s in the cooler suburbs to the low 70s downtown. On Tuesday, we start the day comfortable and sunny but we may notice an increase in cloud cover and humidity by late in the day as a wind from the south returns. An isolated shower or thunderstorm can not be ruled out (20% chance). Confidence: Medium

By Jason Samenow  | July 24, 2010; 5:00 AM ET
Categories:  Forecasts  
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Next: Records fall, and it feels close to 110


remember the snow? here's a place where it never melts!

stay cool.

Posted by: walter-in-fallschurch | July 24, 2010 7:38 AM | Report abuse

CWG, since weather forecasters are posting a heat/humidty index as as high as 110-115 today, can you post a "guess the maximum h/h index for today"? Especially since h/h indexes above 110 are (mercifully) rare hereabouts.

The temp where I live in Glover Park never dropped below 82 this a.m. (restless night!). This isn't an all-time record high DCA minimium temp (which was 84) but probably is the highest low for the date (previous record is 79 degrees).

@Walter, I am going to print one of your snow sculpture photos later today, press it my forehead and see if it has a cooling karma.

Yesterday's max temp of 98 didn't occur 'til 4:48 p.m. Wasn't there one time this summer when the daily high didn't happen 'til after 5 p.m.?

So much for cooling off during cocktail hour.

Posted by: JerryFloyd1 | July 24, 2010 7:56 AM | Report abuse

Do any local weather historians have an answer to this one: We've had a record winter in terms of snowfall, followed by a record summer in terms of heat. Are these kinds of weather extremes normally paired so closely?

All I have to go on is memory but it seems like the heavy winters were always followed by mild summers, though I've only been in the DC area for 16 years.

Posted by: dalison | July 24, 2010 8:22 AM | Report abuse

What is the record for the number of days in a summer that the temperature reached or exceeded 100 degrees in Washington?

Posted by: mike1956 | July 24, 2010 8:38 AM | Report abuse

@Mike1956; there were six 100 or more high temps in 1980 but a couple of weeks CWG posted a larger number (8??) for a year in the 1930s.

Posted by: JerryFloyd1 | July 24, 2010 9:23 AM | Report abuse

Already 90 degrees at DCA; can never remember that happening this early in the day.

Posted by: JerryFloyd1 | July 24, 2010 9:27 AM | Report abuse

Jerry, I agree, it's wasting no time today. Leesburg, and DCA are at 90 by 9am, BWI at 89, and Frederick leading the way at 93!

Posted by: Brian-CapitalWeatherGang | July 24, 2010 9:34 AM | Report abuse

Ahhh, Walter...many thanks. Ice cream pie in the works for today. No sweating for the cook and cool treat for the hubby.

Posted by: tbva | July 24, 2010 9:42 AM | Report abuse


No--the probability of having a record hot summer (of course, a cool August could change that this year) and record snowy winter in the same year is really low and there is no precedent.

Posted by: Jason-CapitalWeatherGang | July 24, 2010 9:52 AM | Report abuse

This morning's low at Reagan National appears to have been 81, breaking the prior record high low temp of 78 from 1987.

Posted by: Jason-CapitalWeatherGang | July 24, 2010 10:04 AM | Report abuse

mike1956, the record is 11 in 1930. Second is 7 in 1988. Only 7 yrs (prior to this one) have had 4 or more.

Posted by: Ian-CapitalWeatherGang | July 24, 2010 10:13 AM | Report abuse

JerryFloyd1, the 91 at midnight made me interested in similar stats so I pulled numbers on every 102+ day at DCA (that's as far back as I can get hourlies). The 90 @ 9 is indeed quite warm it seems, though not a first. Two other days had it in the 102+ cat, they finished 102 and 103. The avg 9 a temp for a 102+ days was 86. This list is pretty incomplete still, I'm going to try to build it back to all 100+ days at DCA.

Posted by: Ian-CapitalWeatherGang | July 24, 2010 10:18 AM | Report abuse

Just got home from a quick library run; now I don't have to go outside again. It's hideous out there, but just barely worse than at 2am this morning. I'm planning on eating sorbet all day.

Posted by: maralenenok | July 24, 2010 10:30 AM | Report abuse

#Ian, thanks as always for your great research. You've provided a lot of valuable and interesting info, and I save some it in Excel spreadsheets, as I'm sure others do.

I think the earliest-in-the-day DCA 100 degree reading was at 12 noon. But my memory is relative...

I do, however, remember one Saturday in 1988 when it was 104 degrees and I walked 2 1/2 miles uphill from downtown to Glover Park. Ah, to be that heat-tolerant again.

Posted by: JerryFloyd1 | July 24, 2010 10:30 AM | Report abuse

One thing: don't rely on OCM, talking news heads, etc. for historical data. An OCM (who I won't name) said this a.m.that the previous record low temp for this date was 79 and I parroted that info in a post above. CWG nailed it at 78.

A couple of days, a newscaster said we had had 34 90-degree days this year. But a couple of days ago it was already up to 38 (yesterday made 40, according to Messrs. Ryan and Hill, who I do trust).

And of course a lot of sources (including this a.m.'s Post weather page) reported yesterday's high at 97, when it was actually 98. However, the high reading occured at 4:48 p.m., which, as noted, is rather late in the day.

I've said before and will say again: you find the most accurate, reliable weather data right here.

Posted by: JerryFloyd1 | July 24, 2010 10:47 AM | Report abuse

clarification re: above (10:47 a.m.)comment:

right here = CWG. They nail it 99+% of the time and on the rare occasions when they don't, a correction is made posthaste.

Posted by: JerryFloyd1 | July 24, 2010 11:11 AM | Report abuse

Thx Jerry, it's been fun playing with the stats since I got the info. I could probably spend my whole life with them though heh! At some point I hope we'll make various parts available easily here so it can be easily referenced. BTW, I think we're right 99.5% of the time, lol.

Posted by: Ian-CapitalWeatherGang | July 24, 2010 11:46 AM | Report abuse

@dalison...It happens. Back in 1936 many localities from Wisconsin to the Dakotas had their coldest February and their hottest July the same year.

We also had an EXTREMELY RARE social/meteorological event last night--a well-attended dance with NO THREAT of rain or severe weather whatsoever! For folks like tominmichiganpark and the rest of the much-needed rain crowd...just put a huge swing dance on the schedule...and you will get downpours such as Milwaukee and Chicago have been having recently---seven inches in Milwaukee on Thursday; eight inches in Chicago last night! We're starting to see rain threats from Tuesday on as some of Bonnie's moisture approaches the area.

One other item...I seem to have lost the picture on the Weather Channel here on Comcast Arlington. Is it just my TV or is Comcast somehow trying to make us push for their merger with TWC owner NBC??? The sound is perfect on ch. 27 picture! Anyway I can still get AccuWeather and the Storm-7 team on 204.

Posted by: Bombo47jea | July 24, 2010 11:48 AM | Report abuse

Without going into the details of radiation balance, specifics of soil type, vegetation, etc, etc, it's possible to calculate the maximum possible summer temperature now in the Metro region (exclusive of climate change).

Drum roll please: 120-125 deg F.

Posted by: SteveT-CapitalWeatherGang | July 24, 2010 12:20 PM | Report abuse

Bombo - I'm in Rosslyn and noticed the same condition for the Weather Channel last night. But I just turned on the TV and it's fine now. Maybe some kind of intermittent problem.

And maybe I was influenced by expectations of how bad it would be out this AM but actually felt it wasn't so bad on my run earlier.

Posted by: marathoner | July 24, 2010 12:35 PM | Report abuse

@walter-in-falls-church: Thx for the reminder! :D

Posted by: --sg | July 24, 2010 12:49 PM | Report abuse

@Ryan - thanks!

@Bombo47jea - I just returned home from So. Cal. When I left LGB airport it was 67F and lightly raining. The shock to my system has been a tad on the high side.

Posted by: dalison | July 24, 2010 1:32 PM | Report abuse

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