Saturday, August 11, 2012

July 2012 hottest month in US history.. extends warmest 12 month period on record

July 2012 has finished as the hottest month in the contiguous US since national records started in 1895, according to recent figures from the National Climatic Data Center. The national monthly average of 77.6F in July 2012 was 0.2F warmer than the previous hottest month of July 1936, set during the great Dust Bowl era.  The month was dominated by hot and dry conditions over most of the US, with the heat mainly centered over the Great Plains through the midwest and Ohio Valley into the mid Atlantic seaboard.  Seven states recorded their 2nd warmest July on record on a statewide average.

The record hot month extended the persistent warmth that began last summer, with the last 12 months now standing as the warmest 12 month period in the US since 1895. The average US national temperature over the last 12 months has been 56.1F (13C), or about 3.3F above normal. Previous to this year, the warmest 12 month period was Nov 1999 to Oct 2000 which averaged 2.7F above normal at 55.5F. The record warmth has also been occurring north of the border as well. Winnipeg has recorded 13 consecutive months above normal dating back to July 2011, and the last 12 months (August 2011-July 2012) have been the warmest 12 month period on record since records began in Winnipeg in 1872. Prior to this year, the warmest 12 month period in the city was from Nov 1877 to Oct 1878, thanks to the record warm El Nino winter of 1877-1878 (still the warmest winter on record in Winnipeg)  

Graph of national US temperature
anomalies since 1895.   Note how much
warmer 2012 has been to date, warmer
than any other similar period since 1895.
In addition, the year to date average of 56.4F so far in 2012 is the warmest Jan-July period ever recorded in the US, easily beating the previous warmest Jan-July period of 1998 (at 54.5F) The graph left shows how dramatically warmer this year has been to date, especially with the warm winter and spring that has made this year warmer than any other corresponding period in US history (since 1895 anyways)  In Winnipeg, our year to date average through the end of July 2012 is 4.0C, tying 1987 for the warmest year through July. (1987 stands as Winnipeg's warmest calendar year with an average of 5.4C.)  For more details on the exceptional warmth of July 2012 and the past year, see blog entries from Dr Jeff Masters and climate historian Chris Burt.              


  1. Hi,


    I've heard rumblings of a large scale cool down later next week which could have our temps dip quite cool for this time of the year with GFS apparently going with near freezing temps as our overnight lows next weekend.
    Not sure if I believe that at this point.

    What's your opnion on this?

  2. Definitely looks like cooler weather later this week, but still unclear how cool and how long it will last. Euro shows us warming up again over the weekend, which would mean a temporary shot of cooler air with lows likely in the single digits (but not near freezing) Could be just a glancing blow of cooler air rather than a prolonged pattern change.. but still too early to say at this point.

  3. Are we really going to get some storms with all this cloud, or is this cloud unexpected and therefore no more storms now?

  4. Thunderstorm activity not expected today over southern Manitoba. A few showers pushing across the RRV through midday, with some clearing coming in from the west this afternoon. Latest radar showing some slightly stronger echoes in a band south of Carman but no lightning detected.

  5. While most of the city seems to have had rain this morning with 2 mm at your station Rob, not a drop has fallen in south St.Vital

  6. Radar confirms that most of the echoes this morning pretty much missed southeast Winnipeg, either passing to the north and west or dissipating by the time they got there. Last line of showers passing through the city right now.. perhaps this one will give St Vital some rain.

    Some lightning strikes also showing up now with cells southwest of Gimli, southwest of Elm Creek and over northern MN south of Sprague.

  7. Good downpour in Headingley heading east over the city. Last batch of showers then we should gradually clear out behind it.

  8. Perhaps the cooldown is wishful thinking from those who prefer extremes a la 1936. A DustBowl year, with a Hot July to go with extremes greater than + and - 40C.