Barnstable Harbor - Great Thatch Island UV IndexUnited StatesMABarnstable CountyBarnstable Harbor - Great Thatch Island1-Day3-Day Graph Plots Open in Graphs UV Forecast NOAABarnstable Harbor - Great Thatch Island UV forecast issued today at 1:05 am. Next forecast at approx. 1:05 am.Get WillyWeather+ to remove ads