How do I know the wind will be favorable? I have purchased a historical climatic archive from NOAA, which catalogues past weather data from hundreds of stations worldwide. There are 12 stations along the route selected as data points to give a representation of the windfields to be expected. My conclusion is the most favorable time of year is May - June when strong SSE winds flow up from the Gulf of Mexico. This direction provides me with an optimum point of sail -a broad reach most of the way. Wind direction also varies with the frontal systems moving through at the time.
The following tables are taken from the Brownsville, TX station, illustrating a favorable wind direction and frequency during the month of May.
For comparison, I have downloaded the daily surface wind reports of the Great Plains from April 29 through June of this year. Based on my analysis of these charts, the wind prevailed from a favorable direction and at speeds that would allow me to maintain a 45-mile per day average.