I use small marker lights mounted under the dash where they can't be seen from the seats but the lights from them softly covers the floor area. This makes it easy to see around the cab. I have a blue set and a purple set in my Rav4 each on their own switch. Around town I usually have both sets on, but out in the dark and lonely, just the darker purple lights are a better choice. I don't like low powered LEDs on the outside of cars, so I don't know enough about them to make a suggestion, but any that don't get hot should do in this type of installation.
If mounted right and if the lights you choose are not too bright, they should be good for most weather conditions, but being able to switch them off is a good plan.
And like Xauterus, I want to see out. On dark nights the dim setting on my clock was so much brighter than my dash lights, even in its dim mode, I installed a switch to turn off the clock.
