Climatological Background  During September, the Northern Hemisphere monsoon systems in West Africa, South Asia, and southwestern North America begin their retreat southward following the maximum solar heating which approaches the equator at the time of the equinox (September 21).  Spring has begun in the Southern Hemisphere, with mid-latitude storm tracks losing strength.

Monthly Mean Temperature (1961-1990), data from the Climate Research Unit, University of East Anglia

DATA: Univ. of East Anglia

Monthly Mean Precipitation (1961-1990), with data from the Climate Research Unit, University of East Anglia

DATA: Univ. of East Anglia

Temperatures Over Land

Few locations saw below average temperatures in September while above average conditions continued to be widespread.  Details:

Africa:  Above average temperatures were seen over most of the continent north of the equator.  Only South Africa had below average temperatures for the month.
Europe:  Central and western sections including France, the United Kingdom and the Baltic States had unusually high temperatures during September.
Asia:   Unusually warm conditions prevailled from Iran and the Caucasus eastward, including much of China, Manchuria, and Japan.
Australia:  Temperatures were well above average across most of the interior sections of the continent.
North America:  The southwestern United States and northern Mexico had above average temperatures.  Alaska and northeastern sections of the country were the only areas with below average temperatures.
South America:  Temperatures were below average across southern Argentina and Chile with near average conditions elsewhere.
 
 
 

Temperature Difference from the 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS.

NOAA NCEP CPC CAMS anomaly temperature anomaly

Precipitation

Africa:  Supplemental data to the map below indicates that irregular rainfall resulted in  below average accumulations across much of West Africa and the Sahel.  In East Africa, below average rainfall continued across much of Tanzania, Kenya, and southern parts of Ethiopia and Somalia.  Above average rainfall was seen mainly across central Africa, especially the Democratic Republic of the Congo.
Europe:   Unusually dry conditions prevailed across much of northern Europe. 
India:  Unusually heavy rainfall in southeastern and northeastern sections produced flooding.  Meanwhile, below average rainfall was seen across central areas and in the northwest - which experienced its second year in a row with significant moisture deficits.
Southeast Asia:  An unusually strong monsoon coupled with tropical storm activity contributed to torrential rains and flooding in large sectionsd of Cambodia, Vietnam, Laos and Thailand (based on supplemental data).
South America:   Early rainfall in southeastern Brazil helped to ease long-term rainfall shortages.  Unusually heavy rain was also seen across sections of northwest Brazil and southern Columbia.
North America:  The eastern and southeastern United States and the Pacific Northwest had usually wet conditions, while below average precipitation in central and southern areas continued.  Much of Mexico saw below average rainfall for the month.
 

Precipitation Difference from 1961-1990 mean, with data from NCEP Climate Prediction Center, CAMS-OPI.

NOAA NCEP CPC CAMS_OPI v9906 anomaly Precipitation Anomaly (mm/day). Contours 0.5, 2, 4, 6, 8,...

Oceanic Conditions

 Tropics:  La Niña (colder than average) conditions have all but vanished in the equatorial Pacific. Above average temperatures continued in much of  the Indian Ocean and western North Pacific,  while more modest above average conditions continued in the tropical Atlantic.
Midlatitudes:  Unusually warm water  persisted in northwestern sections of the North Pacific.  Above average temperatures in the central North Atlantic continued .

Monthly Sea Surface Temperature Difference from the 1950-1979 mean, with data from the Environmental Modeling Center, NCEP/NOAA.

IGOSS NMC monthly Sea Surface Temperature Anomaly