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Changes in climate may allow some nonnative plant species, insect pests, and pathogens to expand their ranges farther north as the climate warms and the growing season increases. The abundance and distribution of some nonnative plant species may be able to increase directly in response to a warmer climate and also indirectly through increased invasion of stressed or disturbed forests. Similarly, forest pests and pathogens are generally able to respond rapidly to changes in climate and also disproportionately damage-stressed ecosystems.

Given that warmer temperatures and seasonal changes in precipitation are expected across the region, it is reasonable to expect that soil moisture regimes will also shift. Longer growing seasons and warmer temperatures would generally be expected to result in greater evapotranspiration losses and lower soil-water availability later in the growing season, thereby increasing moisture stress on forests. Further, increases in extreme rain events suggest that greater amounts of precipitation may occur during fewer precipitation events, resulting in longer periods between rainfall.

All global climate models agree that sea level will rise. Sea levels have increased over the past century, and this trend is expected to continue. Additional warming is expected to increase global sea levels by up to 1m (3 ft) by the end of the century. In the Mid-Atlantic, sea-level rise is significantly greater than observed global sea-level rise, due to sinking of the land surface as it adjust to the melting of former ice sheets and the withdrawals of natural resources from underground.

Heavy precipitation events have increased substantially in number and severity in the across the Northeast over the last century, and many models agree that this trend will continue over the next century. Under the higher scenario (RCP8.5) the number of extreme events is projected to increase by two to three times the historical average in every region by the end of the 21st century, with the largest increases in the Northeast. Under the lower scenario (RCP4.5), these events are projected to increase by 50%–100%.

Seasonal differences in temperatures across the Mid-Atlantic and Northeast have decreased in recent years as winters have warmed three times faster than summers. By the middle of this century, winters are projected to be milder still, with fewer cold extremes, particularly across inland and northern portions of the Northeast. Warmer temperatures are expected to cause more winter precipitation to be delivered as rain. Snowfall, snow depth, and snow pack are all expected to be reduced.

Evidence at both global and local scales indicates that growing seasons have been getting longer, and this trend is projected to become even more pronounced over the next century. Warmer temperatures will result in fewer days with minimum temperatures below 32°F and a shorter freeze-free season. Winter or early-spring warmth has caused plants to start growing and emerge from winter dormancy earlier in the spring.

Temperatures in the Mid-Atlantic region (and across the broader Northeast) are projected to increase on average by 5.27 to 9.11 °F by the end of the century (2070 to 2099), with the greatest warming expected to occur during summer and fall. More warming (9.11 °F) is projected under a high climate scenario (RCP 8.5) and more moderate warming (5.27 °F) is projected under a moderate climate scenario (RCP 4.5).

Climate models under a high emissions scenario indicate temperatures will increase by 4.5F° to 10°F by the end of the century, whereas climate models under a low emissions scenario project temperature increases from about 3°F to 6°F by the end of the century.

Impact models agree that many temperate species will experience increasing suitable habitat and biomass across northern Wisconsin and western Upper Michigan, and that longer growing seasons and warmer temperatures will lead to productivity increases for temperate forest types. The list of species projected to increase includes shagbark hickory, black cherry, bur oak, white oak, and a variety of minor southern species. Models also indicate that deciduous forest types have the potential for large productivity increases across the Upper Midwest.

Impact models agree that boreal or northern species will experience reduced suitable habitat and biomass across the Upper Midwest, and that they may be less able to take advantage of longer growing seasons and warmer temperatures than temperate forest communities. Across northern latitudes, it is generally expected that warmer temperatures will be more favorable to species that are located at the northern extent of their range and less favorable to those at the southern extent.