Interpolated Values are not the same as original data

[AndrewLewin]

I am trying to create contours of the day at which the Growing Degree Day of 650 is reached.  For instance, if the GDD of 650 is reached on day 40, then the contour line would show 40 as well as other values within the study region.

My problem is that when I interpolate the point layer, the resulting values are way off.  I assume it is because of the algorithm used; however, I cannot display the data when the numbers change.  I would like to display the data as countours for their original values.

How do I do this?  Your help is very much appreciated!

Andrew

[TonyPagani]

If your point data is fairly dense and evenly spaced, you could use the Point to Raster tool to create a raster whose cell values are derived from the point(s) which fall within the cell. Set the cell size of the output raster to the average spacing between the points. This should give one point per cell.

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00120000002z000000.htm