It has received positive reviews from critics and features original lyrics about Gendron's mother's death, environmentalism, and lullabyes.

[4] In Exclaim!, Vish Kanna rated this release an 8 out of 10, stating that the "weary and uncompromising" songs on it are "about the foundational elements we work with whenever we must rebuild our ruined selves".

[6] Bruce Miller of PopMatters gave Mayday a 7 out of 10, stating that Gendron has shown growth as a performer since her previous albums.

[7] In Spin, Reed Jackson rated Mayday an A–, stating that Gendron's exploration of a proper recording studio and several backing musicians enhanced the music on this release and "With her remarkable voice—slippery, shadowy, haunted by the ghost of itself—and dolorous melodic sensibility, Gendron renders whatever she's feeling (grief, awe, bittersweet joy) as a complex continuum.

[8] A June 4 overview of the best albums of the year so far at Stereogum included Mayday at 24 and James Rettig wrote that Gendron "pulls from traditional folk songs and other people's poems and blends them in with a mythic imagery all her own, and she's bolstered by master-class musicians that build out the uncomplicated pure centers of her songs".