Compare / definitions
Four summers, four jobs
A useful comparison does not ask which definition is “the real one.” It asks what each definition is for, what starts or ends it, and what evidence can support it.
| Lens | Boundary | Useful for | Does not prove | Evidence posture |
|---|---|---|---|---|
| Astronomical | Solstice/equinox geometry | Sun–Earth seasonal geometry and daylight framing | That local weather is warm today | Physical mechanism · NASA |
| Meteorological | Full calendar months; NOAA uses June–August for Northern Hemisphere summer | Consistent climate statistics and comparison | That every location shares the same ecological phase | Statistical convention · NOAA |
| Ecological / phenological | Observed life-cycle timing | Tracking plants, animals and seasonal biological change | A universal fixed start date | Observation series · USGS / phenology practice |
| Cultural / lived | Local calendars, holidays, practices and symbolic cues | Understanding design, memory, ritual and everyday meaning | A physical mechanism or climate norm | Context / interpretation |
Hemisphere check: astronomical seasonal phase is opposite across hemispheres. The NOAA meteorological-month example shown here is explicitly the Northern Hemisphere convention described by the cited source.
Sources: NASA Science · Helio and You: Seasons on Earth, Mars, and Beyond · NOAA National Centers for Environmental Information · Meteorological Versus Astronomical Seasons · U.S. Geological Survey · Remote Sensing Phenology