My conclusion was that the Environ+ is not really designed for outdoor use as it stands as the electronics is not protected or coated. I bought an enclosure similar to the one shown in the previous post which is an outdoor enclosure with a clear top and I will cut out the bottom panel so that air will circulate around inside. I can then mount it with the open panel pointing downwards.
I use a RPi 3 but connect to the Environ+ using a short ribbon cable.so that should get over the issue of the heat from the RPi causing problems. If I do find it an issue, I may have to have a separate enclosure for the Environ+
If you look at how the professionals do it, they have special enclosures with slated walls to allow air to circulate.
In the future I may look at getting waterproofed measurement sensors but they have to be individually connected and it would take more time and effort to get it working.