"'Tis the Season for Love" for "Chuck's" Sarah Lancaster in this romantic holiday movie. Brendan Penny also stars. 8 p.m. Hallmark Channel
Bill Nye the Science Guy and former Gov. Arnold Schwarzenegger are here to pump — clap! — you up for the fight against climate change on a new edition of "Explorer." 8 p.m. National Geographic Channel
"The Librarians" are back for a new season of fantastical adventures — wait, why are whispering? Rebecca Romijn, John Larroquette and Noah Wyle star. 8 and 9 p.m. TNT
Eureka! The new six-part series...