Spring in the United States is marked by seasonal transitions from cold winters to warmer temperatures, fostering plant growth and outdoor activities. Average temperatures range from 40°F to 70°F (4°C to 21°C), with regional variations. States in the South, such as Florida and Texas, experience earlier springs, while New England and the Upper Midwest see later springs due to colder winters. Planting seasons begin in March or April, depending on USDA hardiness zones, and allergy symptoms peak in late spring as trees and grasses pollinate.

The timing and severity of spring in the U.S. are influenced by climate patterns like the North American Oscillation (NAO) and polar vortex dynamics. Data from the National Oceanic and Atmospheric Administration (NOAA) shows that March 2023 had an average U.S. temperature of 46.1°F (8.4°C), slightly above the 20th-century norm. This warmth accelerated planting schedules, with the USDA reporting a 15% increase in early corn planting in 2023 compared to 2022. Regional disparities are evident: California’s central valley saw blooms 10 days earlier than usual, while Michigan experienced a 2-week delay.

Allergy season, driven by pollen levels, typically starts in March in the South and peaks in late April to May in the Northeast. A 2022 study by the American Academy of Allergy, Asthma & Immunology found that 50% of U.S. adults report worsening symptoms during spring, linked to rising CO2 levels accelerating plant growth. Economically, spring tourism contributes $1.2 trillion annually to U.S. GDP, per the U.S. Travel Association. Safety concerns include increased thunderstorms and flooding; NOAA’s 2023 spring outlook predicted 20% more severe thunderstorms in the Midwest than average. These factors collectively define spring as a period of ecological renewal, agricultural productivity, and public health challenges.