Nino region 1+2, farthest to the east,  is the first to shift to cooler temp anomalies from cooler sub surface water rising to the surface there first. 

We can see the tiny area of cooler blue, just off the coast of South America, along and just south of the equator. Off the coast Ecuador. 

The subsurface water profile ensures La Nina coming quickly and robustly:

All the models pass quickly thru neutral to La Nina over the next several months.

Same link as the other data above:

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

Historically, El Nino's have resulted in better growing weather in the Cornbelt and La Nina's worse weather:

The discussion related to La Nina coming on strong this Summer was here and has not changed:

https://www.marketforum.com/forum/topic/101854/#101858

https://www.marketforum.com/forum/topic/101854/#101859

https://www.marketforum.com/forum/topic/101854/#101860

Here's the latest ENSO discussion. La Nina appears to be coming on fast and strong!

https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

The Eastern, Tropical Pacific is cooling but still some plenty warm waters in the tropical  Atlantic below. Watch out hurricane season when combining that with a La Nino(that helps suppress upper level Atlantic wind shear that rips apart hurricanes)

Cooling fast in some places below

Heat content in the Central/East is plunging very fast.

Very impressive sub-surface cool anomalies with this cooler water rising to the surface early in a developing La Nina.

Here's one of the models with the maps to the right.  Rapid transition to a La Nina this Summer. Historically, that's not a good thing for our growing season. It can also mean heat and CDDs for natural gas. Also increases chances for more active tropical Atlantic basin activity.  El Nino's cause more upper level wind sheer downstream in the Atlantic.  This damages the best wind profile needed for ideal hurricane dynamics.