How to test desert (Dubai-like) conditions when you are in a temperate climate
The usual approach is to use an environmental chamber to control the temperature. Humidity can also be controlled with many or most commercial environmental chambers, but usually high humidity is of concern so there are means to increase the humidity in the chamber by means of evaporating water and measuring Rh with something like a wet bulb/dry bulb hygrometer. Relative humidity will drop as the same volume of air + moisture is heated, of course. See the below psychrometric chart from this website: 



But, as I say, usually low RH is not too much of a concern. It can increase the likelihood of ESD (which you should protect against anyway) and change the mechanical size and characteristics of hygroscopic materials such as polyamide (nylon) but usually it's benign or advantageous. 

Direct sunlight can cause damage to plastics and other materials and cause high temperatures to occur within an enclosure. I've seen manufacturers of products simply put their products outside in the sunlight for a few months and monitor the deterioration. There are solar simulators but they are not that common for ordinary electronics testing, at least in my experience. 

You can easily hack the controlled increase in temperature with an enclosure, a temperature controller and a sensor, plus a heater. An ordinary incandescent bulb can serve as a heater. I have a device like that made to sterilize N95 masks, which has almost zero in materials. A commercial environmental chamber might cost $15K, more if you need to simulate high altitudes as well as temperature and humidity.