DOI: 10.3886/e233228v1
title: Climate.gov Data Snapshots: SST - ENSO Region, Monthly Difference from Average

description: <b>Q: Do sea surface temperatures suggest El Niño or La Niña conditions?
</b><b>
 </b><br><b>A:</b> Colors
 on this map show where and by how much monthly sea surface temperature 
differed from long-term average (1985-1993, details from Coral Reef Watch).
 Red areas were warmer than average, and blue areas were cooler than 
average. The darker the color, the larger the difference from the 
long-term average. White and very light areas were near average. [Editor's
 note: All maps are based on the 1985-1993 climatology. Due to a 
processing glitch, maps prior to September 2021 are incorrectly labelled
 as using a base period of 1981-2010. If correcting this date is 
important for your use, you can rebuild the image with the assets in the
 full-resolution zip file.] 

Warmer-than-average sea surface temperature across the central and 
eastern tropical Pacific is one of the indicators of El Niño conditions.
 El Niño is the name for the warm phase of a major climate pattern 
called the El Niño Southern Oscillation (ENSO).
 Conversely, cooler-than-average sea surface temperature across this 
region is one indicator of La Niña conditions. La Niña is the name for 
the cool phase of ENSO.

 
 <br><b>Q: Where do these measurements come from?
</b><b>
 </b><br><b>A:</b> These monthly measurements are made from NOAA's CoralTemp sea
 surface temperature (SST) data. Every day, instruments on eight 
satellites in two different orbits (geostationary and polar) measure sea
 surface temperature by checking how much energy is radiated by the 
ocean at different wavelengths. Computer programs plot these 
measurements on a gridded map and then merge and smooth the data into a 
gap-free product using mathematical filters. Each grid point covers an 
area approximately 5 x 5 km. Daily temperatures at each grid point are 
averaged together to calculate monthly average temperature. 

To calculate the difference-from-average temperatures shown here, a 
computer program takes the monthly average temperature at each grid 
point, and subtracts the long-term average for that month. If the result
 is a positive number, the sea surface was warmer than the long-term 
average. A negative result from the subtraction means the sea surface 
was cooler than usual.

 
 <br><b>Q: What do the colors mean?</b><b>
 </b><br><b>A:</b> Shades
 of blue show locations where sea surface temperature was cooler than 
its long-term average. Locations shown in shades of orange and red are 
where the sea’s surface was warmer than the long-term average. The 
darker the shade of red or blue, the larger the difference from the 
long-term average or “usual” sea surface temperature. Locations that are
 white or very light show where sea surface temperature was the same as 
or very close to its long-term average.

 
 <br><b>Q: Why do these data matter?</b><b>
 </b><br><b>A:</b> Water
 covers more than 70% of our planet's surface. Tracking the temperature 
of the sea’s surface helps scientists understand how much heat energy is
 in the ocean and how it changes over time. In the tropical Pacific 
Ocean, differences from normal sea surface temperatures serve as one of 
the major indicators as to whether ENSO is in an El Niño or La Niña 
phase. These phases can have dramatic impacts on weather across the 
tropics and the mid-latitudes. Sea surface temperature anomalies give 
scientists a way to monitor the evolution of ENSO phases, enabling them 
to predict potential impacts in the Pacific region and around the world 
weeks in advance.

 
 <br><b>Q: How did you produce these snapshots?</b><b>
 </b><br><b>A:</b> Data
 Snapshots are derivatives of existing data products: to meet the needs 
of a broad audience, we present the source data in a simplified visual 
style. NOAA's Environmental Visualization Laboratory (NNVL) produces the
 Sea Surface Temperature Anomaly files. Maps are centered over the 
central and eastern tropical Pacific Ocean, the area scientists monitor 
for the oceanic development of El Niño and La Niña events.

 
 
 
 <br><b>References</b>
 
 NOAA NNVL Sea Surface Temperature Anomaly (SSTA)<br>
NOAA NNVL SSTA FTP access<br>
NOAA Coral Reef Watch<br>
CoralTemp data<br>
CoralTemp climatology (long-term average)<br>
CoralTemp climatology methodology
 <br>Source: https://www.climate.gov/maps-data/data-snapshots/data-source/sst-enso-region-monthly-difference-aver...<br><br><br><br>
description: Data is divided in to folders by image resolution -- full size (zip), small (png) and large (png). Occasionally there may be one image missing in a particular size but available in another size.<br><br>Data downloaded from climate.gov 6/17/2025.