It's always amazing to see the spectacular clusters of Monarchs at their overwintering grounds. This page at Journey North has lots of related information. But iNaturalist reports that the severe late-winter storm in Texas did wreak havoc on the first part of the northward migration path:
The 11-day cold spell (10-20 February) in Texas was a disaster. Freezing temperatures covered the state and extended well into Northern Mexico. While many of the immediate effects of the freeze are clear, season long and multiple year effects may linger. The damage to the flora was extraordinary, and it is likely that nearly all above ground insects died over a wide area. Plants already in flower may have been so damaged as to not flower this year. We are seeking help to record that damage and the recovery of plants that flower in March along with the appearance of milkweed shoots and buds. Both are resources used by monarchs returning from Mexico in mid-March. We also need help recording the number of returning monarchs. ALL monarch observations are of value. How well the monarch population will develop in 2021 will be determined by the March conditions in Texas.
The link provides information on how citizen scientists can contribute data.
This updating map shows where Monarchs have been sighted so far this year.