JACKSONVILLE, Fla. – The dry season in Jacksonville typically begins in late October and lasts through early May. This seasonal transition is marked by a noticeable drop in humidity and precipitation as colder, drier air masses start moving into the region.
Dewpoint levels play a crucial role in this transition, as they signal moisture reduction in the air. Once dewpoints consistently fall below 60°F, it indicates the onset of drier conditions, a hallmark of Jacksonville’s dry season.
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In North Florida, the dewpoint is a better indicator of the dry season’s arrival than air temperature alone. This year, Jacksonville has seen slightly above-average dewpoints in late September and early October, which delayed the onset of drier conditions compared to last year.
According to NOAA, this year has resulted in 60.19 inches of rain, marking a 12.2″ surplus so far through October 22. Jacksonville International Airport recorded a total of 58.81 inches of rain in 2023.
The bulk of the rain comes during Florida’s long, hot, humid summer.
As Jacksonville moves deeper into the fall, the dry season will become more apparent, with fewer rainy days and cooler evenings as dewpoints continue to drop.
According to NOAA historical climate data, November is Jacksonville’s driest month, with an average rainfall of about 2.03 inches. This significant reduction in rainfall marks the peak of the dry season as the atmospheric patterns shift and bring more stable, less humid air to the region. November’s low precipitation levels are influenced by high-pressure systems that dominate during the fall, pushing away moisture-laden tropical systems that are common in the summer.
The end of Jacksonville’s rainy season is driven by several meteorological features that create drier conditions.
- High-Pressure Systems: As fall progresses, a subtropical ridge of high pressure begins to weaken across the southeastern U.S. These high-pressure systems are linked across the Atlantic to the Azores during the summer but break down in October allowing drier air to head south.
- Cold Fronts: Cold fronts are a major feature in the transition to the dry season. As these fronts sweep southward from the continental U.S., it brings cooler and drier air to Florida. The passage of each cold front further lowers dewpoint levels, signaling the drop in atmospheric moisture. These fronts act as barriers that block moisture from the Gulf of Mexico and the Atlantic, effectively ending the frequent thunderstorms of the summer season.
- Jet Stream Shifts: During the rainy season, the jet stream (a fast-moving current of air high in the atmosphere) is typically positioned farther north, allowing tropical moisture and storm systems to move into Florida. As the jet stream shifts southward in the fall, it helps steer tropical disturbances away from the region, contributing to the end of the rainy season and reducing the potential for hurricanes.
- Trade Winds and Subsidence: In the transition to the dry season, the trade winds, which bring moist air during the summer, weaken. Subsidence (sinking air) increases, leading to less cloud cover and precipitation.
Together, these features mark the end of Jacksonville’s rainy season.