This is probably the single most important piece of equipment. You can use it to protect you from the blazing sun, as well as rain. Often the races will continue in the rain or a rain shower will pass in 20 minutes or so. It would be a shame to miss a day of great racing, when this simple tool can protect you from discomfort. The large beach umbrellas are even permitted at most race sites.
Even on cloudy days th damaging sun's rays will still get you. Remember that you will be on the waterfront with the sun reflecting off the water.
The kind that are cloth and fold up into a bag are best. These folding chairs have four separate legs, which prevents rocking on uneven ground. A chair with a built in sun shade (cabana style) is even better, but you can use an umbrella for the same sun protection. Usually there is enough room in the carry bag for your chair to carry additional items, such as umbrella, sunscreen, etc.
The weather may vary during the day, as with a passing shower or cloudy skies. It is best to layer your clothing, so that adjustments can be made to keep yourself comfortable throughout the day. If you find yourself needing an extra layer at the race, there is usually a vendor selling T-shirts, sweatshirts, or hats. Again, we want you to be comfortable and it's great to support the vendors as well.