1. Peak of Hurricane Season
"All the ingredients necessary for tropical development come together in late August, September and October," AccuWeather Expert Senior Meteorologist Dan Kottlowski said.
Creating the perfect recipe for tropical development, warm water temperatures, favorable upper-level winds and less dry air make late summer and early fall the ideal time for hurricane formation.
"Environmental conditions which have thus far prevented development will continue," Kottlowski said. "We can probably expect a few more organized tropical systems into September and October."
Throughout the summer, water temperatures continue to rise in the Atlantic Ocean hitting their warmest temperatures and peaking in September. This increase in water temperature coupled with the transition of Africa's spring non-tropical waves to tropical waves in late August become the main driving force behind early fall tropical development in the ocean.
The westerly winds shift more northward in August and September, promoting upper-level winds that are favorable for tropical development. Additionally, unlike the early summer months, the presence of African dust is limited and the air becomes less dry in the late summer.
All of these factors combined with the right conditions can create the ideal scenario for a hurricane to form as proven by Superstorm Sandy last October.
"Around this time, it's often possible to see a lot more development," Kottlowski said.
2. Early-Season Snowstorms
Snow in the fall season brings dangers of its own as many trees are still adorned with their fall colors. Early-season snow is not light and powdery but instead heavy and wet, not only bad for avid skiers and snowboarders but also for power lines.
"With leaves still on trees, snow adds more weight to trees and power lines making them more prone to collapse," AccuWeather Meteorologist Brian Edwards said. This could result in power outages and road closures.
Already in September, snow has blanketed portions of the Rockies and High Plains. Six to eight inches of snow accumulated across portions of the Black Hills in South Dakota, and Cut Bank and Lewistown in Montana, marking the season's first snowfall.
With the potential to create hazardous driving conditions and travel delays for early morning commutes, fog is third on the list for fall weather's biggest threats.
"Fog is a product of longer, cooler nights and lower overnight lows," Edwards said. Fall is the ideal time for the formation of fog as there are lower nighttime lows, cooler temperatures overall and lower humidity that can more easily meet the dew point.
Fog is can last for multiple hours on end and is usually most dense in the fall months in river valleys.
4. Early Frost
"The biggest threat into the fall for frost is outside cities in the rural areas," Edwards said. Inside most cities the pavement is typically warm, and this can prevent early frost from occurring but out in more rural areas, pavement is not as prevalent.
The Northeast is forecast to receive a frost this week, weeks earlier than normal. Temperatures may dip to their lowest levels since the spring, potentially ending the growing season for some farmers.
"An early frost could kill sensitive crops before they have finished the growing cycle," said Edwards.