Weather Forecast for Whitney PortalThe above link is the forecast for an altitude of 8689'. The campground is around 7900', so it might be a little warmer there.
Here's a forecast for 6822' nearby
http://www.wrh.noaa.gov/forecast/MapClic...tField2=-118.16 .
Since the campground is roughly halfway between these two in elevation, take the average of these two for the campground temps. (Of course, if you want to you can interpolate but these forecasts aren't that accurate anyhow.)
For example, tomorrow Tuesday the high at 8689' is forecasted at 63F. The high at 6822' is forecasted at 79F so the estimated forecast high at the campground 7900' would be roughly halfway between these two using this method, i.e. 71F.
If anyone reading this happens to be there tomorrow Tuesday, you might check the high temp at the Portal Store or the campground and see how it compares to these forecasts.