St. Bartholomew brings the cold dew.

The proverb treats Saint Bartholomew as a marker for a seasonal change: dew that once felt mild now feels cold in the morning.

It expresses an expectation that warmer weather is beginning to give way to cooler conditions, rather than predicting the weather on one exact day.

Use it to remark on cool, damp mornings as the warm season wanes. It suits a conversation about seasonal signs, not a precise forecast for a particular date.