The lapse rate referred to by fishmonger is the ADIABATIC LAPSE RATE. It is a good rule of thumb to use for your intended purpose, but not a "rule of law" since it assumes certain things remain constant, which they never do. There are also several variables that change this lapse rate. Google it to find out more. Having said that, the "average adiabatic lapse rate" is 3.3F/1000 feet. So, for ease of calculations, Lone Pine is ~ 3500', the portal is ~ 8,500', and the summit is ~14,500'. At 1:00 AM temp in Lone Pine is "likely" 70, so temp at Portal is "likely" 70 - 3.3*5 = 53.5F. I will leave it to you to estimate the duration of your hike in order to estimate the temp at the summit, but as others have said you will not likely be hot.
