The overhead camera shot of the school shows clear grass on the field. But in the shots of it behind Cisco and Caitlin, there is frost on the ground.
Cisco and Chester sometimes have visible exhalations, and sometimes not, despite the fact that it is supposedly December.
Although it's December 4, there is no snow in sight (although there is frost on the ground in some shots, and Cisco and Chester occasionally have visible exhalations) and everyone is wearing at best light-weather gear. Central City and its environs are in the Midwest or the East Coast.
The submarine gives off a foghorn noise, as confirmed by the closed captioning. While it may seem counter-intuitive, submarines DO, in fact, have a "foghorn." It's technically called a "ship's whistle," and it is exposed while on the surface, and fully enclosed for submersion . And, yes, it sounds just as one might expect a foghorn to sound.
In December 1998, the Blockbuster store is advertising that "Practical Magic" is guaranteed in stock, but that film's home video release wasn't until at least February 1999.
Cisco states that the Still Force works like Turtle 2.0's powers. However, the Still Force works in reverse, as Turtle 2.0 could accelerate or steal time from targets to age them to death.