Please only use the charger that came w/ your chromebook or an authorized replacement from Dell (replacements are available at school). Other chargers may not meet safety regulation. There are many 3rd party chargers that have different output voltage and current ratings, and may use poor quality components.
Chromebooks are a school tool and not a charger for cell phones and other devices. Some devices, especially new high speed USB C cables, can cause damage to the Chromebook battery and void the warranty.
Chromebooks and all other tech tools should not be subjected to extreme temperature, hot or cold. Please take extra care with regards to temperature fluctuations. If the Chromebook has been left in the cold, do not power it on until it has been brought inside and adjusted to room temperature