One barrier to the adoption of evidenced-based teaching practices may be that faculty do not see teaching as an important part of their identities as professionals. Graduate school is a key time for professional identity development, and currently we know little about how doctoral students develop identities as college teachers. In this qualitative study, we aim to characterize the factors that promote and hinder teaching identity among 33 life sciences doctoral students with diverse career interests at one research university. We collected data using semi-structured interviews and analyzed it using qualitative analysis closely aligned with grounded theory. Our analysis involved iteratively and collaboratively analyzing interview transcripts while considering existing literature about socialization and professional identity and remaining open to novel ideas in the data. From this analysis, we developed a mechanistic model of the factors that influenced teaching identity in our participants. Independent teaching experiences, teaching professional development, and teaching mentors contributed to salient and stable teaching identities among doctoral students. Being recognized by faculty as a teacher was also important, but rare. The professional culture that doctoral students perceived acted like a blizzard that they had to navigate through to develop a teaching identity. This culture strongly valued research over teaching, resulting in a sometimes cold and isolating environment for students interested in teaching. The culture also made it harder to see existing opportunities for teaching development and made it more challenging to move toward these opportunities, much like the deep snow and driving winds of a blizzard. The mechanistic model described in this work is an important first step in understanding how doctoral training influences teaching identity. This model serves as a hypothesis that should be tested and refined through additional empirical work across contexts.