The weather in early March is usually well-suited for running. The temperatures range from the low 40’s or high 30’s at the start, to the 70’s at the finish with a 75% chance of sunshine. The first half of the race is usually run under a high fog with the sun breaking through in the late morning. Occasionally there is a slight tailwind early in the race and a slight headwind late in the morning. There is a slight possibility of rain, so be prepared.
To date, rain hit the second half of the marathon course in two years, 1991 and 2000. In 2001, 2006, 2009 and 2011 there were rain and high winds throughout the race. In 1998, 1999, 2002, 2003, 2004, 2005, 2007 and 2008 the conditions were ideal: a slight tailwind for the entire course, cold air and sunshine.
Use your favortite website to check the current weather conditions in the Napa area - Napa (94558) or Calistoga (94515).