(Radio Iowa) – As many as 60-thousand cyclists are expected on today’s (Wednesday) leg of RAGBRAI from Ames to Des Moines, which would be the largest-ever day on the bike ride — and on one of the hottest days of the year so far. A heat advisory is posted for Iowa’s southern half and western Iowa as forecasters say the heat index may reach 105 degrees. Hans House, an emergency medicine professor at the University of Iowa Hospitals and Clinics, says people who are most vulnerable to heat stroke are the very young, the very old, and those on certain medications. “So a lot of elderly are on medications, either for blood pressure or for Parkinson’s or other psychiatric medications,” House says, “and all of these can adversely affect the body’s own heat regulatory mechanisms.”

House says signs of heat stroke include people who are hot, but who aren’t sweating, and are showing signs of an altered mental state like confusion. She says, “Since part of heatstroke is that change in mental status or that confusion, you may not recognize that you’re getting yourself in trouble, especially with the dehydration part.” The experts say to skip strenuous outdoor activities and if you have to be outside, drink plenty of water and take frequent breaks in the shade. That won’t be an option for most RAGBRAI riders as they head for Iowa’s largest city. Many of Des Moines’ main roads are closed to accommodate bike traffic with limited pass-through points for cars.

Des Moines Police Sergeant Paul Parizek says motorists should plan to take detours or to take extra time to get around today. “Our whole city is probably going to be impacted by an increased number of cyclists,” Parizek says, “so we need to make sure we keep our heads on a swivel and share the road and do everything we can to make sure they get where they need to go safely.” Parizek says the most issues may be on East 14th Street which will be completely closed from Euclid to University Avenue.

“That’s a main thoroughfare through our city,” Parizek says. “It’s a state highway and it’s going to be shut down for a long time, beginning up in Ankeny all the way into Des Moines, so that’s where we’re going to see the biggest impact.” Cyclists will take Des Moines’ Walnut Street through downtown, and Fleur Drive to Water Works Park where riders will camp overnight. Parizek says road restrictions will last until 6 o’clock tonight or later. Around 100 Des Moines police officers are working the RAGBRAI route to manage traffic throughout the city.