Rains are mainly in short bursts in the afternoon, so may have little, or no impact on your safari. But you can expect temperatures to be quite hot, with an average day temperature of 27 degrees Centigrade.
Birding can also be excellent in March, with migratory birds present. However this is not the best time to see game in Etosha, as mentioned above, it can be harder to see it at this time.
Despite not being peak for wildlife, March can often be busy, depending on the dates for Easter. It is a popular family destination, for good reason, so families often choose the Easter Holidays as a time to escape urban life and embark on a Namibia adventure.
March is not the best time in regards to seeing wildlife in Etosha, but it can be a great time to travel for birds, unique landscapes, and good prices.