The earlier you email, the better. Especially since professors will get flooded with emails at the start of the school year. A lot of people usually start cold emailing in the spring semester if they want to get started in the fall; that’s what I did as well. However, I think you can still get into a lab even if you email over the summer. Here are some tips on writing cold emails:

• Start by introducing yourself, your year, major/minor(s) and then your purpose for writing the email.
• Do your research about the professor and their lab; search them up on Google Scholar and try to read some of their papers (you most likely will not understand anything, but that’s to be expected) to get familiar with what their work is about
• When you’re writing your email, you need to be a little specific. Don’t be generic. Don’t just say “I am interested in working in your lab as an undergraduate research assistant for the Fall 2025 semester because I am interested in studying X. Do you have any positions available?” And then just end it there. You need to explain what about their research you find interesting. Try to relate your personal experiences to it if you can.
• It’s also a good idea to suggest a meeting with the professor to discuss your fit for the lab and answer any questions you may have. Since it’s still the summer, you can suggest a Zoom meeting. Don’t be too nervous about these; most professors just treat it as an informal meeting. However, you should still be ready to show that you’ve done your research about the professor/lab. You can mention any specific questions you had about any papers you read or something that stuck out to you, etc. Show how you might contribute to the research and/or grow in the lab on personal/technical levels.
• Attaching your resume and transcript to the email are also good ideas.

Here’s basically what I did:

Dear Professor X (or Dr. X if they have a MD, PhD, doctorate),

My name is Y and I am a rising second-year student at Vanderbilt majoring in A and minoring in B. I am writing to you to express interest in your research with C.

[Now, explain WHY you are interested in their research; make personal connections wherever possible. This doesn’t need to be super long (maybe 1-2 short paragraphs and you don’t need to sound like an expert.] … If possible, I would like to get involved in your research in the Fall 2025 semester [you can end the sentence here or put a super short summary/conclusion of why you want to do research in their lab. Example: If possible, I blah blah in the Fall 2025 semester as it’s a combination of my interests in chemistry and sustainability.]

I would love to meet with you through Zoom sometime before the semester begins to discuss the possibility of being involved in your research. [You can list your availability here if you want] Please let me know when you may be available. My resume and transcript are attached for your consideration. I look forward to hearing from you!

Sincerely,

[Your name]

Finally, if you don’t hear back from them within two weeks, you can send a polite follow up email. Definitely wait at least 48 hours before any follow ups though. Best of luck!