May at last. Maybe we can finally shake April's drizzle and chill. This month ends our risk of frost. Baltimore's latest trace of snow fell May 11, 1951. Average daytime high temperatures at BWI Marshall Airport climb from 69 to 79 by month's end. The average lows rise from 47 to 57. Record highs reach 98, while all-time lows linger in the 30s until the 30th. One of Baltimore's oldest record lows is 34, on the books since May 1, 1876.