  Inspired by the recent evidences of nano-Hertz stochastic gravitational waves
observed by the pulsar timing array collaborations, we explore their implied
supercooled electroweak phase transition in the singlet extension of the
Standard Model. Our findings reveal that by adjusting the model parameter at
per milli level, the corresponding percolation temperature can be continuously
lowered to 1 GeV. With such a low percolation temperature, the singlet dark
matter may freeze out before the electroweak phase transition, and,
consequently, the entropy generated during the transition can significantly
affect the dark matter relic density. It alleviates the tension between the
requirement of a strong electroweak phase transition and the constraints
imposed by dark matter direct detection, and can be tested in future
experiments.
