The pre-Jacob's Trouble-rapture is imminent, which means it can happen any time and it's not dependent on signs and events.
1 Thessalonians 5:3 is meant for AFTER the rapture.
Read it in context:
2 For ye yourselves know perfectly, that the day of the Lord shall come, even as a thief in the night.
3 For when they shall say, Peace and safety, then shall come upon them sudden destruction, as the travail upon a woman with child, and they shall not escape.
4 But ye, brethren, are not in darkness, that that day shall come on you, as it were a thief.
Those who are saved by the undeserved GIFT of God's GRACE through FAITH alone in the atoning BLOOD of JESUS and His resurrection from the dead on the third day, according to the scriptures, 1 Corinthians 15:1-4, are ALWAYS RAPTURE-READY!