Since it is spring I have been going down to he beach. Temperature is about 40 - 50 degrees with a 10-20 mph wind blowing. I noticed that after being out in that weather for 30 minutes or more I become lightheaded. I may walk around a little but I am certainly not overexerting myself. Once I am back inside for an hour or so the lightheadedness dissipates.
I have had an MI, over ten years ago, and I do have CAD.
Comments appreciated. Thanks.

donsabi,
A hypothesis:
We can probably assume your cardiac output isn't up to snuff. Being out on a chilly windy beach probably diverts more of your blood supply to areas that need to be warmed. Add a little exertion and the muscles call for their share. Maybe the brain experiences a slight deficit especially if there is some narrowing of the carotid artery.

Are you on any BP meds? If so, why not bring your BP tester to the beach and check your blood pressure when you feel lightheaded. That might shed some light.

Lenin,
Thank you!
Taking my BP monitor with me is an excellent idea. I will do that the next time I go to the beach.

Lenin,
I checked my BP before and after cold exposure.
127/66 before and 132/67 afterwards. There really isn't much difference.
Maybe it's time for a stress test.
I take Altace 2.5mg, Tenormin 25mg for BP and heart.

donsabi,
The Tenormin (atenolol), though a light dose, can EASILY make you lightheaded with exertion.