Monday, June 28, 2010

New Daily Record Heat Extends Washington June Temperature Record

June 30, Midnight Update: The low of 67° has held through midnight, so the final record-breaking June average is 80.6°.

June 30, Late PM Update: The June 30 high is in at 81°. If the low of 67° holds, the month goes into the books at a record-blasting average of 80.6° (charts to be updated when final figures available).

With today's high above 80°, there were only 3 days this month which failed to reach at least 80°. This is the smallest number for June since 1996.

Despite the pre-canned assertion elsewhere that "highs below 80 seem likely in many spots", Washington Dulles and Baltimore also reached 80° or above for the day, with Baltimore Inner Harbor at 84°.

Regionally, even Martinsburg WV (80°) and Hagerstown MD (84°) achieved the Big Eight-Oh-Plus. In fact, as of 5 pm, these additional secondary reporting stations in Maryland and Virginia were all above 80°: Winchester, Frederick, Leesburg, Staunton, Aberdeen, Culpeper, Blackskburg, Fredericksburg.

June 30, PM Update: Following yesterday's high of 92° and low of 78°, the June monthly average reached 80.8°. Today's high so far of 78° and low of 67° virtually assure that the final June average will be at least 80.5°, which is a remarkable 1.1° above the old record.

The histogram chart of all June average temperatures from 1871 through 2010 shows how far an outlier this month has been. Each bar represents the number of times the June average was in a given 0.5° range. The point at the far right of the chart shows the 2010 average in the 80.5°-81° bucket. The 2010 value is an impressive 2.8 standard deviations above the overall average.

June 30, 1 AM Update: The temperature is 78° at 1 am, so the 80° low won't hold, but it didn't miss by much.

June 29, Late PM Update: Despite a north to northwesterly breeze, the temperature is still holding at 90° as of 7 pm.

June 29, PM Update: The final high and low for the 28th were 97° and 73°, respectively. As of 2 pm, today has already reached 92°. This is the 18th day with 90°+ this month, which is apparently a new June record. The morning low was 80°, but that is likely to be surpassed by midnight (technically, 1 am EDT).

The monthly average through yesterday is 80.6°. That will increase if the low later today is anywhere above 70°, but it will go down a little with lower temperatures tomorrow.

June 28, Midnight Update: Here are some more June 2010 heat records:
  • Richmond has reached 102° 3 times this month; previously 102° had been reached no more than once in June
  • Philadelphia's monthly average to date is within 0.1° of the June record high
  • Philadelphia's 14 days with 90°+ is within 1 of the June record
  • Atlantic City's 13 days with 90°+ exceeds the June record by 2
June 28, 6:30 PM Update: Added records for Richmond, Elizabeth City NC, and Wallops Island VA below.

June 28, 5:30 PM Update: The high was 97° at 1:27 pm; the low is being reported as 70°, but this is inconsistent with the time shown of 8:56 am. The high was 3° short of the daily record, but Baltimore set a record of 99° (old record 98° in 1969). This is now the 3rd daily high set this month in Baltimore, tying the 3 each in June 1925 and 1994. Baltimore has also tied a record high a record high on the 23rd and a record high minimum on the 24th.

Richmond blew away its 1959 record by 3° with a high of 102°. Richmond records began in 1871. Elizabeth City NC tied a record at 97°. Wallops Island VA, where records only began in 1963, smashed the 2001 record of 94° with a high of 98°.

This is the 17th day of 90° or higher temperatures at Washington this month, which reportedly ties the June record set in 1943 and 1994. An expected high in the low 90s tomorrow would break the record. There have also been 7 days of 95° or higher; there were only 5 days 95°+ in 1994 and 3 in 1943. In 1981, the previous 3rd warmest June, there were 9 days of 90°+ and 4 of 95°+.

June 28, 4 PM Update: The Washington temperature dipped at least as low as 73° during the thunderstorm. If that remains the low for the day, the June average to date will be 80.6°.

June 28, 2:30 PM Update: The temperature at Dulles has already dropped in a heavy thunderstorm to 79° from a high of 94°. Meanwhile, the temperature at Washington National rose to at least equal the high of 96° before the storm.

June 28 PM Update: Strong thunderstorms moving into the area will drop the temperature, but the high so far today is 96° as of 2 pm. The low so far of 81° would break the daily record for high minimum, although it's likely to be breached. Assuming the low holds, however, the monthly average to date would rise to an even 80.75°.

Original post:
A new daily record high temperature of 99° for June 27 at Washington, DC has further extended the June monthly average into record heat territory. The previous record for the date was 98° in 1980.

With the morning low of 75°, the June average to date is now 80.5°, over 1° above the old record of 79.4° in 1994. This is a greater margin than the difference between June 1994 and the current 3rd place holder, June 1981. Although a cool-down is likely by Wednesday, this month is now virtually assured to clinch the record with the first June in history to average above 80°.

There have now been 16 days this June with highs of 90° or above. With a forecast high in the mid 90s, Monday will likely tie June 1994's count of 90°+ days.

The high of 100° at Baltimore also set a record, exceeding the 99° in 1952. Richmond's high of 102° exceeded the old record of 100° in 1952.

For earlier history of this month's record temperatures, see here.

Images (click to enlarge): Distribution of Washington, DC June average temperatures from 1871 to 2010; June 2010 daily temperatures vs. average and record; June 2010 average temperature vs. previous 10 warmest Junes, June and July monthly averages; CapitalClimate charts from National Weather Service data, background images from Kevin Ambrose


S.P. Gass said...


"is likely to be surpassed by midnight (technically, 1 am EDT)."

Does this mean that daily temps are calculated on a standard time basis year round?

CapitalClimate said...

Yes, for consistency they are always calculated on local standard time. (Remember that the dates of daylight time have changed over the years.)

With the temperature still at 90° at 6 pm, however, it's going to have a hard time dropping a lot more than 10° in the next 7 hours.

A Siegel said...

Remember, of course, that there was a lot of snow ...

It is not at all surprising George Will's silence in the face of the sweltering heat (not even to complain, at least in public, sweating at a baseball game).

It is shameful the WashPost's silence and inability to link Washington's temperature record and changing weather patterns to a discussion of what is happening globally and climate change.

PS: Thank you for your work.

CapitalClimate said...

After WaPo's Big Fail with their earlier A1 heat wave story, they pushed it off to the Metro section on Tuesday and garbled the statistics by focusing on the number of 90+ days. The real story is in the average temperature; breaking the monthly record by such a large amount is really a big deal.

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