May 1 (Labour Day) is a public holiday. And so is May 22 (Buddha's birthday).
You'd be unlucky to be here for a typhoon at the beginning of May. Perhaps the odd thunderstorm... Authorities do their best to keep the airport open; it's too important to have closed for long.
You'd a lot less unlucky to have rain - we get around 300mm rainfall in May and 15 days on average. Fog should be less common.