Can I put my tank outside?

Generally not a good idea...

DEF will freeze and crystallize at 12°F and can also lose it potency if stored for long periods of time with temperatures over 86°F. A non-heated bulk tank should be stored inside. Senergy does offer Heat Trace and insulation options if outside winter storage is required. If storing outside in non-winter locations we recommend an awning type cover to help control the heat.