The El Nino phase is persisting as expected with sea-surface temperatures remaining warmer than average throughout much of Equatorial Pacific Ocean. Most of the latest long-range climate models indicate that this El Nino will remain in place during the rest of the spring and now possibly through the upcoming summer months.
As for the May temperature outlook, slightly above normal temperatures are projected across the Pacific Northwest. Also, much of the Northeast and Mid-Atlantic are forecast to see slightly above normal temperatures as well, possibly due to effects from a positive NAO (North Atlantic Oscillation) that is expected at least through much of the month of April. A small surplus of early-season cooling degree days of between 20 and 40 is possible throughout these regions of the United States during the month of May.
In contrast, parts of north-central Plains and upper Midwest may see temperatures that average slightly below normal in May due to mainly the influence of the El Nino. A deficit of early-season cooling degrees of between 20 and 40 is forecast across these areas of the United States as a result. If the El Nino persists into summer it will likely influence temperature and rainfall trends across portions of the United States. This will be monitored over the next couple of months.