NEC/safety for proximity of switch to a gas water heater

Can anyone tell me the guidelines (NEC or otherwise) about the proximity of a clock switch and a 60 gallon gas water heater? The wall-mounted switch is 5 feet from the floor, 13 inches to the top of the water tank, and about 4 feet from the burner at the bottom of the heater. If this is out of code I could move the switch, if necessary. This clock switch controls a small 20 watt outdoor transformer for landscape lighting. The mechanical clock switch is on a 20-amp rated GFCI circuit, enclosed in a plastic electrical box, manufactured in 2002, and a cover plate is properly installed. The gas water heater is about 10 years old, the same age as the house. Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.