I have road training/racing tires on my bike that are slick - no tread. I use them rain or shine - and we have some nasty rain here. If you take some general precautions riding in the rain, you should be fine with normal tires.

- Watch out for paint (i.e., center and side lines on roads) - paint gets very slick when wet and you don't want to brake or corner fast on it.

- Same goes for wood or tracks - they get very slick when wet.

- Remember braking distances are increased when wet.

- Careful in puddles that are so deep you don't know what may be concealed under them (potholes, gravel, etc.)

- Don't follow too close to other riders. I know tri's have a no drafting policy but don't know anything about duathlons. Anyway, with braking and reaction distance increased, you don't want to be too close to the person in front.

It's not ideal to get this experience in a race - he should be practicing riding in these conditions on non-race days. But if he is careful about it, he should be okay.