Bitcoin heads into August with a weak track record, a bad sign for holders hoping for a summer rally.

• August has been one of Bitcoin's worst months since 2013, with a median loss of about 7.5%.
• The last four Augusts in a row all closed lower, losing about 10% on average.
• Rare positive Augusts have been strong — one jumped 65% — but those are the exception, not the rule.
• The typical outcome leans negative, so a flat-to-down month is the base case.

Outlook: History points to a weak August for Bitcoin, with losses more likely than gains.