Wh- and w- words cause confusion in English when it comes to their spelling. Here's a useful tip: if it's a question word beginning with 'w-', then it's spelt with 'wh-'. For example: 'what?', 'where?'.
The trouble is that for words beginning with wh, the h isn't pronounced. Where and wear sound exactly the same. Not only do some people get the spelling wrong - they also get the word completely wrong. It's fairly common to see whether and weather mixed up! Here's a little phrase to help you remember what both mean.
As you can see, the two words are in alphabetical order ~ weather before whether. If you memorise this little phrase, it might help if you are unsure. Try this 11-plus quiz and see how well you do with 'wh-' and 'w-' spelling. By the way: question words are followed by a '?' and the meanings of the other words are given in the brackets.