During the past month, sea-surface temperatures have remained near average throughout much of the Equatorial Pacific Ocean. Any warming that was developing across the eastern Pacific has subsided in recent weeks. Latest climate models continue to indicate this neutral phase is expected to persist through the upcoming summer months.
As for June, expect warmer than normal temperatures across portions of the south-central Rockies, south-central Plains, lower Mississippi Valley and Deep South. Early-season cooling degree-day surpluses of between 30 and 90 are predicted across these regions. There are some indications that parts of the Pacific Northwest and northern Rockies could see cooler than normal June temperatures. As a result, monthly cooling degree-day deficits of between 30 and 60 are projected along with slightly lower than average early-season cooling costs. On a whole, temperatures are forecast to average closer to normal across the northern Plains, Midwest, Great Lakes, Northeast and Mid-Atlantic regions.
The North Atlantic Oscillation (NAO) index has become positive during the past couple weeks. If the NAO remains positive for an extended period, a warmer than normal weather pattern could set up across the eastern third of the country by early summer.