When does autumn start in 2026?

2 min reading time

Autumn starts on 1 September if you follow the meteorological calendar, and on 23 September 2026 if you follow the astronomical one. Both are correct, they just measure different things. That is why weather forecasters talk about autumn from the first of the month while your calendar app waits another three weeks.

The two dates explained

Meteorological autumn always runs from 1 September to 30 November. It splits the year into four tidy three-month blocks, which makes it easy to compare weather data between years. The date never moves.

Astronomical autumn begins at the September equinox, the moment the sun crosses the celestial equator and day and night are close to equal length. In 2026 that falls on 23 September. It shifts by a few hours each year, which is why the equinox lands on the 22nd or the 23rd depending on the year.

What changes indoors

The practical shift is light. From late September the days shorten quickly, and rooms that were bright all summer start getting a few hours of weak light instead. Houseplants notice this before you do. Growth slows, and the amount of water they need drops with it.

Heating is the other change. Radiators dry the air out, which is hard on tropical plants but barely registers for succulents and cacti. Closed terrariums are largely unaffected, since the sealed glass keeps its own humidity regardless of what the central heating is doing.

Getting your plants through it

Three adjustments cover most of it:

Water less. Cut back roughly by half from October, and check the soil rather than sticking to a schedule.
Move plants closer to the window as the light drops, but keep them off cold sills at night.
Stop feeding until spring. Plants are not growing much, so extra nutrients just sit in the soil.

Autumn is also when indoor gardening picks up again, simply because there is less to do outside. A DIY terrarium kit is a reasonable way to spend a wet weekend, and a closed bottle garden needs almost no attention through the darker months. If your rooms lose most of their daylight in winter, artificial plants keep the green without the struggle. For terrariums that have been running a season or two, a refill kit and a few basic plant care tools are usually all they need before winter.

In short

If you want one date, use 1 September. If you want the astronomical one, autumn 2026 begins on 23 September. Either way, the useful signal is the light, and that is what your plants will respond to first.

FAQ

When does autumn start?

There are two answers, and both are correct. Meteorological autumn always runs from 1 September to 30 November, which is what weather forecasters use. Astronomical autumn begins at the September equinox, which in 2026 falls on 23 September.

When do the clocks go back in 2026?

On Sunday 25 October, when the clocks go back an hour and the evenings suddenly get dark much earlier. It's the point in the year when most people notice the change in light indoors, and it's a good moment to move plants closer to a window.

Why do leaves change colour in autumn?

As days shorten, trees stop producing chlorophyll, the green pigment that powers photosynthesis. The yellows and oranges were in the leaf all along and simply become visible once the green fades. Reds are made fresh in autumn, which is why some years are more colourful than others depending on the weather.

When is Halloween 2026?

Saturday 31 October. Most people decorate in the last week of October, and pumpkins are best carved two or three days before, since a carved pumpkin doesn't last long.

How long does a carved pumpkin last?

Usually between five days and two weeks, depending on how warm it's kept. Drying the inside thoroughly after carving, keeping the pumpkin outside in the cold and using a battery light rather than a candle all make a noticeable difference.

Should I carve a pumpkin from the top or the bottom?

The bottom. It keeps the stalk intact, hides the join, and lets you set the pumpkin down over a light instead of reaching in through a lid. It also drains better, which helps it last longer.

What can I do with a pumpkin after Halloween?

If it's still firm, use it as a temporary planter. Line the inside, add a little soil and sit succulents or small cacti in it, since they need so little water that the pumpkin stays firm for weeks. Once it softens, compost it and move the plants into a pot.

Why are my houseplants struggling in autumn?

Almost always because of light, not care. Shorter days mean slower growth, so plants use far less water and any fertiliser just sits in the soil. From late September, water around half as often, stop feeding until March, and move plants closer to the window.

When should I bring outdoor plants inside?

Before the first frost, and earlier for anything tender. As a rule of thumb, bring tender plants in once night temperatures start dropping towards ten degrees. Check the leaves and undersides for pests before they come indoors, since a warm house lets an infestation spread quickly.

How do I make my home feel autumnal without filling it with decorations?

Work with texture rather than seasonal colour: glass, wood, moss, dried stems and linen in a narrow range of greens and browns. Choose one focal point where you actually look, and add a warm side lamp for the evenings. Three well-placed things read better than fifteen scattered ones.