RodneyS

New records also at DCA (74) and IAD (71).

Yes indeed. It's interesting that the lowest DC daily January maximum is quite a bit higher than either December's or February's (now 65, on February 3, 1927), at a relatively balmy 68 degrees (on January 3rd, in both 2000 and 2004). At Dulles, it's a different story, as January 10th (2002) is the lowest daily maximum temperature on record, at a mere 58 degrees. Today's high of 72 at IAD easily broke the previous February 7th record of 65 degrees, but the lowest February daily maximum there remains 63 (in both 1990 and 2001). In December, the lowest IAD daily maximum is also 63, set on December 19th (1967).

This January was a different story at DCA, rising to an average temperature of 42.1 degrees vs 41.8 in December 2016. The January average was 12th warmest of all-time in DC, and was 6.1 degrees above the 1981-2010 normal.

The high minimum records at both airports should also fall by day's end. At Dulles, the current record is just 38, set in 2007. Today's low there is currently 49, and is very likely to hold. In DC, the current record is 47, set in 1890. Today's low at DCA is currently 51, and is also very likely to hold.

No contest at Dulles, as today's high of 70 easily eclipsed the previous record of 63 set in 1995. DCA's 72 didn't break the 1890 record of 76, but was the warmest January 12th in DC since that year.

2016 will be the new # 2 in DC, at 60.3 degrees (actually 60.4 if you compute the true 366-day average, rather than averaging the 12 monthly averages). And IAD will also be #2 all-time, at 57.1 (vs. 57.9 in 2012).

Meteorological autumn (September 1-November 30) also was a record setter at DC/DCA, with an average temperature of 63.9 degrees vs. the previous record high of 63.3 in 2007. IAD came up just short, with an average temperature of 60.0 degrees vs. the record high of 60.3 in 2007.

I just discovered that the September 2016 DCA average minimum of 68.6 broke the all-time DC record of 68.2 set in 1881. On the other hand, the September 2016 DCA average maximum of 83.4 didn't even approach the 1881 record of 88.2. In fact, this year's September average maximum was slightly below last year's (83.5) and ranks only 13th all-time.

September 2016 was also a record-setter at IAD (73.1 vs previous record of 72.7 in 1998) and tied for third at DC/DCA (76.0 vs 78.2 in 1881, 77.1 in 1980, and 76.0 in 1930).

You're welcome, and as you have noted, the DCA record of 81.7 for the 1980 astronomical summer is suspect, as it exceeded the IAD temperature of 76.1 by 5.6 degrees. So, a faulty DCA sensor may have been a significant factor in that record.

Astronomical summer (June 21-September 23, on average) was record-setter at IAD (78.0 vs previous record of 76.8 in 2010) and second at DC/DCA (81.1 vs 81.7 in 1980). Also, composite summer (June 1-September 23) was record-setter at both (IAD: 77.1 vs previous record of 76.5 in 2010 and DC/DCA: 80.17 vs previous record of 80.14 in 2010).

It's a longshot at this point, as the 10:52 AM DCA temperature is only 83, vs 88 yesterday at that same time. However, with the old sensor . . .

Yes indeed, good observation -- yesterday was the rainiest August 15th ever in DC. However, 1.16 inches on August 12th would rank as only the 11th rainiest for that day of the year, and so there is still quite a discrepancy between August 12th and August 15th in DC historically. I'm still waiting for some aspiring meterorologist to write his/her Ph.D thesis on this subject.

Yesterday marked the third consecutive 100 degree or higher reading at DCA. The only other time that happened in August in DC was the legendary summer of 1930, which saw August 3-5 do it. If we hit 100 or more today at DCA, that will tie both 1930 (July 19-22) and 2012 (July 5-8) for having the most consecutive days that reached at least 100.

At last, a rainy August 15th at DCA (1.16 inches) and nothing on the 12th. Here are the updated totals, 1871-2016: August 12: 42.55 inches total; 21 days with a trace, 52 days with measurable, 12 days with at least an inch, 5 days with 2+ inches. August 15: 12.28 inches total; 16 days with a trace, 46 days with measurable, 5 days with at least an inch, no days with 2+ inches.

And today marked the 13th consecutive day of at least 90 degrees at DCA, with forecasts tomorrow calling for a high in the mid-80s. Last year we also "officially" had 13 consecutive 90+ readings (during July 24th-August 5th), but that was right before the DCA temperature sensor was replaced on August 10th, with a reference sensor (psychro-dyne) showing a reading of 1.7 degrees too high on the old sensor. Prior to that, DCA had 16 straight 90+ readings July 18-August 2, 2011. The all-time record is 21 straight 90+ readings July 25-August 14, 1980. .

Similar picture for both DCA and IAD, as all three area airports recorded an even 100 degrees. First 100+ at DCA since July 26, 2012, and first at IAD since July 18, 2012. DCA tied the record for July 25th set in 1930 and IAD broke the record of 98 set in 2010.

DCA July 4th maximum of 74 was the lowest since DC's all-time low maximum of 68 on July 4, 1941.

Today marked the 15th consecutive day -- May 24-June 7 -- of a maximum in the 80s at DCA. While the streak is likely over, it did, according to my records, break the all-time DC 80s streak for the first half of the year. I believe that the previous record-holder for that time frame was June 15-28, 1907 (14 days). The all-time record for consecutive days with a maximum in the 80s, I believe, is August 11-September 1, 2001 (22 days).

I have not checked every month in DC history, but I just noticed that May 1953 had 24 days with at least a trace of precipitation at DCA, with 17 days of measurable precipitation there. The corresponding figures for May 2016 are 22 and 19. So, DCA did not exceed the former total this May, but did exceed the latter total.

After failing to reach 80 degrees until May 24th, DCA has now recorded eight consecutive maximums in the 80s. When was the last time that May 24-31 each had maximums in the 80s in DC? Never since official daily temperature record-keeping began in 1872. The closest previously was in 1911, when all but May 30th had maximums in the 80s. However, that day reached an even 90.

Today DCA finally reached 80 degrees in May, the second-latest initial 80-degree May reading in DC history. The latest remains May 26, 1935.

Evidently, the Sunday Dulles report has been corrected to delete the trace of precipitation, and so the official record streak of consecutive days with at least a trace of precipitation there reverts back to 19, April 26-May 14, 2016.

And IAD also tied the record low this morning, but at 36 degrees.

Dulles defied the forecast today and recorded a trace of precipitation, to extend the streak to 20 days.