Yes you can. All our heaters are fully waterproof and weatherproof.
Each heater comes with an IP rating, which you would similarly find on any electrical product that is designed to be used outside.
For example the IP rating could be IP24 or IP65. Now the first number (the 2 or the 6 for example) is not relevant to this question, it applies to dust and particle ingress.
The second number (the 4 or the 5 in these instances) is the water ingress and the number we should pay attention to here.
When looking at a patio heater the second number of the IP rating is usually a 4 or a 5 or perhaps even a 6 or 7.
For an IP rating of 4, the heater would be fine in a shower environment, so any kind of light rain would not be a problem, you could mount it on the wall and leave it there all year round.
In an environment where you are likely to experience heavier rain, for example rain going sideways or even going upwards because it is bouncing off of surfaces or coming off of drainpipes, you would need a higher ingress protection, and that would have to be a 5 rating.
With a 5 rating and that means water can be sprayed at it from any direction without causing damage or harm.
The majority of the heaters from our Shadow range have a water ingress rating of 5, meaning you could put a hosepipe on them without any ill effects.
In fact for heaters near the coast, we recommend that you do put a hosepipe on them from time to time, just to clear away any build up of salt from the air and to keep the lamp clear.