The first thing I do with a netcdf file is type
to see what's inside it. If you have some variables named latitude, longitude, and T2M, read them in like this:
lon = ncread('myfile.nc','longitude');
lat = ncread('myfile.nc','latitude');
T = ncread('myfile.nc','T2M');
Most of the time with NetCDF's of climate data, you'll have to swap the first two dimensions of any gridded data. That probably looks like this:
for 2D data or
if T is a 3D data cube.
Assuming T is 3D where the third dimension corresponds to time, you could contour the first time slice like this:
But you say you want to show T over time. What exactly do you mean by that?