The Iowa caucuses occur every four years in the midst of winters that can be filled with cold and snow. That means the campaign events set by presidential candidates at times take place during snow storms and the highway routes can be clogged with snow or ice.

Iowans got a reminder of that reality on Tuesday, when Braden Joplin, a volunteer for Ben Carson's presidential campaign, died after being hospitalized with injuries suffered in a car wreck in western Iowa.

That crash occurred when a van carrying three Carson volunteers and a paid staffer flipped onto its side on an icy road and was hit by another vehicle. The other three workers were injured. Joplin, 25, attended Texas Tech University, and many of the 15 presidential candidates gave quick condolences.

Republican Mike Huckabee was the first candidate to come through Sioux City following the sad death. I asked him Thursday about how candidates juggle the desire to meet as many people as possible with trying to keep safe during travels. Presidential candidates typically plan out events days in advance, when the weather ahead may not be known.

Huckabee said safety governs all decisions on whether to hold to a campaign event during poor winter conditions.

"There is no event that is worth taking a chance with....We have to put the people first," Huckabee said.

He said he immediately sent an email to all campaign workers reminding them to be careful, and if they encounter dicey driving conditions to pull back and wait for a better time.  Huckabee noted some of the staffers are not from Iowa and may have limited experience in driving on snow.

He told the workers, "We want to run with every ounce of energy...but put your safety first."

Huckabee said the weather during his Iowa stops during the 2015-16 winter months have worked out well, as no bad conditions have necessitated cancellation of a planned event.

Six days ago, Marco Rubio planned three Iowa stops. Rubio made the first one near Des Moines on Saturday, then due to wintry weather cancelled one in Spencer, Iowa, before making it on time to Sioux Center, where 600 people turned out.