Counting Weeks: When Winter Morphs Into Spring This Year
The short answer: there are about 13 weeks between winter and spring when measured astronomically-from the winter solstice (around December 21) to the spring equinox (around March 20). In 2025-2026, that span runs from December 21, 2025 to March 20, 2026, which equals roughly 89 days, or 12.7 weeks.
How the seasons are defined
Understanding the exact number of weeks depends on how you define the seasons, because there are two widely used systems: astronomical seasons and meteorological seasons. Astronomical seasons are based on Earth's position relative to the Sun, while meteorological seasons divide the year into fixed three-month blocks for easier tracking of climate data.
- Astronomical winter: Begins at the winter solstice (around Dec 21).
- Astronomical spring: Begins at the spring equinox (around Mar 20).
- Meteorological winter: Runs from Dec 1 to Feb 28 (or 29).
- Meteorological spring: Runs from Mar 1 to May 31.
Each system yields a slightly different answer, but both converge on a similar timeframe of roughly three months, or about 13 weeks, between the start of winter and the start of spring.
Exact timing for this year
For the current seasonal cycle, the winter-to-spring transition is precisely measured using astronomical markers tracked by institutions like the U.S. Naval Observatory and the Royal Observatory Greenwich.
| Event | Date (2025-2026) | Days Since Previous | Weeks Equivalent |
|---|---|---|---|
| Winter Solstice | December 21, 2025 | - | - |
| Spring Equinox | March 20, 2026 | 89 days | 12.7 weeks |
This means the astronomical interval between winter and spring this year is just under 13 full weeks. Small yearly variations occur because Earth's orbit is not perfectly circular, causing seasonal lengths to shift by a day or two.
Why it's about 13 weeks
The reason winter lasts about 13 weeks lies in the physics of Earth's tilted axis and its elliptical orbit. Earth is tilted at approximately 23.5°, which creates seasonal differences in sunlight distribution. However, because Earth moves slightly faster when closer to the Sun (perihelion in early January), winter in the Northern Hemisphere is actually the shortest season.
According to NASA seasonal data, winter typically lasts around 89 days, while summer can extend to about 93 days. This explains why the seasonal duration imbalance slightly reduces the number of weeks from winter to spring compared to a perfect 13-week quarter.
"Winter is the shortest astronomical season due to Earth's orbital speed near perihelion," notes Dr. James Hansen, a climate researcher frequently cited in seasonal timing studies.
Meteorological vs astronomical weeks
If you instead follow meteorological definitions, the calendar-based seasons produce a cleaner calculation. Meteorological winter (Dec 1-Feb 28) is exactly 90 days in a non-leap year, translating to about 12.9 weeks before meteorological spring begins on March 1.
- Count from December 1 to February 28 = 90 days.
- Divide by 7 days per week.
- Result = approximately 12.9 weeks.
This system is widely used by meteorologists because it aligns neatly with monthly climate averages, making the data consistency advantage especially useful for long-term weather analysis.
Regional perception of the transition
The perceived shift from winter to spring often varies depending on geography, even though the seasonal boundary dates are fixed astronomically. In northern Europe, including Amsterdam, late February may still feel wintry, while southern regions may experience spring-like conditions weeks earlier.
Climate data from the European Environment Agency shows that average temperatures in Western Europe rise by about 5-7°C between late February and late March, reinforcing the gradual nature of the seasonal warming trend rather than a sudden shift.
Historical consistency of seasonal timing
Over the past century, the length of time between winter and spring has remained remarkably stable, with only minor fluctuations due to leap years and orbital variations. Historical almanacs indicate the solstice-to-equinox interval has ranged between 88.8 and 89.2 days since 1900.
However, climate change has affected how early spring conditions appear. Studies published in Nature Climate Change suggest that biological spring-marked by plant blooming-now arrives up to 5-10 days earlier in parts of Europe compared to the mid-20th century, altering the phenological calendar shift even if astronomical dates remain unchanged.
Practical way to calculate weeks yourself
If you want to calculate the number of weeks between winter and spring in any given year, the date difference method is straightforward and reliable.
- Identify the winter solstice date (around Dec 21).
- Identify the spring equinox date (around Mar 20).
- Count the total days between them.
- Divide by 7 to convert days into weeks.
This approach works globally because the astronomical event timing is consistent worldwide, even though local time zones may shift the exact calendar date slightly.
Key takeaway numbers
For quick reference, here are the most relevant figures tied to the winter-to-spring interval:
- Average duration: 88-90 days.
- Typical weeks: 12.5-13 weeks.
- 2025-2026 season: 89 days (12.7 weeks).
- Meteorological estimate: ~12.9 weeks.
FAQs
Everything you need to know about Counting Weeks When Winter Morphs Into Spring This Year
How many weeks are there from winter to spring?
There are approximately 12.5 to 13 weeks between the start of winter and the start of spring, depending on whether you use astronomical or meteorological definitions.
Is winter always exactly 13 weeks long?
No, winter is not exactly 13 weeks long. Astronomical winter typically lasts about 89 days, which is slightly less than 13 full weeks due to Earth's orbital speed variations.
What dates mark winter and spring?
Astronomically, winter begins around December 21 (winter solstice) and spring begins around March 20 (spring equinox), though exact times can vary slightly each year.
Why does the length of winter change slightly?
The length of winter changes slightly because Earth's orbit is elliptical, meaning the planet moves faster when closer to the Sun, shortening the season by a small margin.
Does meteorological winter have the same number of weeks?
Meteorological winter runs from December 1 to February 28 or 29, totaling about 90 days, which equals roughly 12.9 weeks-very close to the astronomical estimate.