One of the first signs you will notice if you have a blood clot, is that the area of skin near the clot may be warmer, than the rest of your body.
This won't be similar to a fever that is commonly experienced in the forehead, as this would be more symptomatic anywhere else in the body. If you have a clot developing in the leg for instance, then you can start to feel a warm sensation near where the clot has formed.
To get past the warm feeling if it is bothersome to the patient is to place some ice in a wash cloth and gently lay it on the area. It is never wise to leave ice on are skin, or to leave it on the area for a very long time frame as it can further irritate the skin.