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.
Addendum: Reposted from March of this year to add this discouraging news about the deterioration of one of the Mexican monarch reserve sites:
"... you and I will never again see La Lagunita as the Bruggers saw it. More consequentially, neither will the monarchs, because during these past 15 months of pandemic-induced deprivation and desperation, La Lagunita has been trashed. Last year, someone — likely impoverished young men from a nearby community — illegally cut down several dozen oyamel firs, hauling them away for lumber. In December, the arriving monarchs tried to form a colony at La Lagunita but failed, according to Ellen Sharp, who runs a monarch-centric hotel at the foot of the mountain.A few weeks later, the monarchs gave up and abandoned La Lagunita altogether, shifting to a different location on the mountain. These migrants had become refugees.Sharp and her husband, Joel Moreno Rojas, have gone to great lengths to try to protect Cerro Pelón from loggers, even forming a nonprofit organization that has hired local “forest guardians” to patrol the mountain and report what they see to the Mexican authorities. But their reports are usually ignored, Sharp says.Last month, the guardians found another six trees felled at La Lagunita. Eight more were cut down a few days later. These latest wounds make it even less likely that La Lagunita will ever again successfully host roosting monarchs...The motivation behind these destructive incursions is sadly obvious. The pandemic has had a devastating effect on the struggling, tourist-dependent communities bordering the 52-square-mile core zone of the Monarch Butterfly Biosphere Reserve, where logging is nominally banned but is now on the rise, reversing years of progress. Reserve officials recently acknowledged that 33 acres in the core zone had been illegally logged last year, up from just one acre the year before. The toll this year will surely be worse.Violence is on the upswing, too, including the unsolved killings of two men who worked at the most heavily visited monarch colony, El Rosario. Now that the pandemic has driven away international tourists, gangs are filling the vacuum..."
More at the link, none of it encouraging.