Antenna will greatly increase your 3G stability and performance by a large fraction and it would greatly minimize the effects of weather on your connection.

Below are 2 types of antenna

Yagi - Designed for a ultra long range receiving, stability is not the original aim of yagi. Users on extreme countryside which totally couldn't get any signal are suggested to go for Yagi

Panel - Designed for stability and performance boosting, it boost the stability if you already on a high speed and minimize D/C. Easy installation/
Suggested for everyone as long as they got the signal.