Is one enough time for prof to write my LOR?

<p>Sorry, I meant to write "one month" in the title</p>

<p>I don't start school until next week so I can't meet in person with my professors until then. My earliest deadline for transfer apps is March 1st.
If I ask my professors for a letter of rec and give them exactly one month till the letter needs to be postmarked, is that sufficient time? Even though the deadline is March 1st I'd like to mail in the letters by around mid Feb, preferably before the 20th.
Or, what if I e-mail them now and give them a heads-up and follow with them in person when I get back to school?</p>

<p>I would give them a heads up now, but a month should be enough time.</p>