Trading term

What is Seasonality?

Seasonality is the idea that a market tends to do better or worse at a certain time of year, like a particular month.

Some seasonal patterns have a cause you can point to. Grain prices move with the harvest, and natural gas with the heating season. Others are just a record of past months, like crypto's "Uptober", the idea that bitcoin goes up in October.

A record alone is weak evidence. With twelve months to choose from, one of them will look good by luck. From 2011 to 2025, bitcoin rose in 10 of 15 Octobers. But when all the monthly changes were shuffled at random into 12 fake months, the best fake month did at least that well 99.8% of the time.

For example

Bitcoin rose in 9 of the 10 Octobers from 2015 to 2024, which is where the name Uptober comes from. It fell in 3 of the 4 before that, and fell again in October 2025.

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Why it matters to you

A seasonal pattern with a real cause can help with timing. One without a cause is often just the luckiest month in a small sample, and it can stop working the year you trade it.

⚠ Picking the best month after the fact

If you look at twelve months and pick the best one, it will always look special. Ask whether a random month could have done as well, and whether there's a reason the pattern should exist.

Frequently asked questions

Is Uptober real?

Bitcoin rose in 10 of 15 Octobers from 2011 to 2025, with a median gain of 11%. July, February and April did as well or better. A shuffle test shows luck alone gives the best month a record like that almost every time.

What is the worst month for bitcoin?

September has the weakest record: up in 6 of 15 years from 2011 to 2025, with a median change of −3.2%. It fell six years in a row from 2017 to 2022, then rose in 2023, 2024 and 2025.

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Related terms

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