Is it normal for two year old to have undescended testicles at times. at times they go up. when other times there in a normal position?

Exam: It sounds like you may be talking about retraction testes. If they are palpable in the scrotum they are not undescended, a good physical exam and discussion with his pediatrician should help clarify.

Retractile testicles: In some boys, the testicles may appear to be outside of the scrotum from time to time, which can raise the concern of an undescended testicle. Some of these boys may have the condition known as retractile testes. This is a normal condition in which the testes reside in the scrotum but on occasion temporarily retract or pull back up into the groin.

Likely to be ok: Yes, it is common for the testicles to be pulled up high in the scrotum due to cold or other stimulation. As long as each of them is "down" some of the time and not permanently up in the abdomen, then there is not likely to be a problem. Ask your doctor the next time you have an appointment. S/he can do a careful exam to be sure that both testicles are "descended".