I have an issue for the result of QGIS Zonal statistics mean values. I expect the value for the polygon marked red (poquoson) is about 26.6 but it seems that it is averaged value over one right shifted cells. Values showing in small black font are mean values for the each polygon according to zonal statistics. Values showing in blue are raster values in us.tmax_nohads_ll_20140525_float.tiff
I made zonal statistics using files with tl_2013_us_county.shp & us.tmax_nohads_ll_20140525_float.tiff on http://www.qgistutorials.com/en/docs/sampling_raster_data.html
1st thing I did was to change CRS for tl_2013_us_county.shp to EPSG4326. I believe that CRS of us.tmax_nohads_ll_20140525_float.tiff and tl_2013_us_county.shp became the same in such a way.
2nd I executed zonal statistics
Platform is QGIS2.18.13 32bit On Windows 10 Pro 64bit Intel Core i5-6500 CPU
Is there any way to get values what I expect?
For above case, expected value is over 26.06 instead of 25.08.