The date on the calendar has not changed. Nature’s schedule has.
In the Northern Hemisphere, spring officially begins with the March equinox. In the Southern Hemisphere, including Brazil, it begins with the September equinox. In 2026, spring will officially arrive in Brazil on September 22 at 9:05 p.m., according to the Observatório Nacional. But the astronomical beginning of the season is not necessarily the moment when nature starts behaving as if winter is over.
Scientists use the term “phenology” to study the timing of recurring natural events, such as when plants bloom, trees produce their first leaves, insects emerge and birds migrate. These events are increasingly being affected by rising temperatures.
A 2026 analysis by the USA National Phenology Network shows just how noticeable these changes can be. In much of the central and western United States, spring arrived between two and five weeks earlier than the 1991–2020 average. In parts of Wyoming, Montana, Colorado, Nebraska, Kansas, Idaho, Nevada and Oregon, the organization recorded the earliest leaf-out in its dataset, which dates back to 1981.
That does not mean that the official date of spring has moved forward. Instead, it means that some of the natural events we associate with the season are happening earlier. Climate Central analyzed the same phenological data in a March 2026 report and found that the first spring leaves are now appearing earlier than they did in 1981 in 88% of 242 major U.S. cities. On average, leaf emergence is occurring six days earlier.
Six days might not sound like much. But when an entire ecosystem depends on different species responding to the same seasonal signals, even small changes can have consequences.
An early spring can be a problem
At first, it might seem like an earlier spring would be good news. After all, who would complain about flowers appearing sooner or warmer weather arriving early?
The problem is that warmer weather does not necessarily mean stable weather.
In a 2024 report for The Associated Press, farmers in the American Midwest described how increasingly unpredictable spring weather is affecting their planting schedules. The story explains that climate change is contributing to wetter and more erratic conditions, leaving farmers with shorter windows to work their fields.
The changes are not only about temperature. According to the report, farmers in Ohio have lost about five days of workable field time in April since 1995 because of increasingly wet conditions. Climate projections cited by AP also indicate that spring rainfall in the Midwest could increase by 8% to 20% by the middle of the century.
That creates a strange contradiction: climate change can make some signs of spring appear earlier, while also making the season itself more difficult to predict. And that is where an earlier or more unpredictable spring becomes more than a matter of flowers blooming a few days ahead of schedule.
A changing schedule for wildlife
Plants are not the only ones adjusting their calendars!
Bird migration is also closely connected to seasonal conditions. Birds rely on environmental cues to determine when to migrate, breed and search for food. But the plants and insects they depend on are responding to changing temperatures too.
A study analyzed 24 years of weather radar data and found that spring migration across North America had shifted earlier. The research was discussed by a senior in a 2020 Forbes article about whether birds are adapting quickly enough to climate change.
The problem is not necessarily that birds cannot change their behavior. Some species are already migrating earlier. The concern is whether every part of the ecosystem can change at the same speed.
Imagine a bird arriving at its breeding grounds earlier, only to find that the peak availability of the insects it feeds to its chicks has already passed. When the timing between species starts to fall out of sync, what scientists call a “phenological mismatch” can occur.
Remember Tinker Bell? Nature needs timing, too
Remember Tinker Bell? In the 2008 Disney movie, the arrival of spring is almost treated like a giant production. The fairies work together to prepare flowers, leaves, seeds and other elements of nature before sending them to the mainland. Every fairy has a specific talent, and every part of the process has to come together before spring can arrive.
Of course, real flowers do not need fairies to bloom. But the movie offers a surprisingly simple way to imagine what happens when something disrupts the process.
Now imagine that the fairies suddenly had to work with a changing schedule. Some parts of their preparation happened earlier, others later, and no one knew exactly when the season would arrive. Even the smallest change could affect what comes next.
That is the part of Tinker Bell that feels unexpectedly relevant to climate change. The natural world does not have a team of fairies coordinating every detail. There is no one making sure that flowers, insects, birds and trees stay on the same schedule.
In Pixie Hollow, the fairies can work together to solve a problem before spring reaches the mainland. In the real world, however, nature has to adapt as the conditions around it change.
And maybe that is the simplest way to think about what climate change is doing to the seasons: it is not necessarily erasing spring. It is making its timing harder to predict.
So, does spring still arrive in spring?
The short answer is: yes, but not necessarily in the way we expect.
Astronomically, spring still arrives when the equinox occurs. In Brazil, that means September 22 in 2026. But biologically, there is no single moment when the entire planet suddenly becomes “spring.”
A tree does not check the calendar before producing leaves. A bird does not know that September 22 is the official beginning of a season. Plants and animals respond to environmental signals such as temperature, daylight and food availability. As those signals change, their schedules can change too.
This does not mean that every spring will be warmer than the previous one or that every flower will bloom earlier every year. Weather naturally varies, and individual species respond differently. The larger concern is the long-term trend: as global temperatures rise, seasonal patterns can become earlier, longer or more unpredictable.
And that can affect much more than our perception of when spring starts. It can influence agriculture, allergies, migration, reproduction and even the relationships between species.
Perhaps that is what makes climate change so easy to overlook. It does not always arrive as a dramatic event. Sometimes, it looks like a tree blooming a little too early, a bird arriving before its food does…
The calendar can keep telling us when spring begins, but nature has never really followed the calendar. Climate change may be making that difference harder to ignore.
———————————————————————————————————————————————————————————————————————
The article above was edited by Elisa Nuñez.
Liked this type of content? Check Her Campus Cásper Líbero home page for more!