Halloween (or Hallowe’en, see here) has in recent years also become a tradition in Europe. For quite some time, I have been wondering what the correct pronunciation of Halloween is.
My usual source, the Longman Pronunciation Dictionary, lists [hæləʊ’iːn] as the standard British pronunciation, and [hæloʊ’iːn] as the standard American pronunciation. The Oxford English Dictionary lists the same two variants, namely [hæləʊ’iːn] and [hæloʊ’iːn], and provides audio recordings for you to listen to. Interestingly, these pronunciations imply that the letter w is silent! Wikipedia suggests that the w can also be audible ([hæloʊw’iːn]), in agreement with the standard reference for American English, Merriam-Webster. For example in German-speaking countries, many people pronounce Halloween as [hæləʊ’wiːn], which basically sounds like “Hello Wien”.
The Longman Dictionary also includes the less common, American variant [ha:loʊ’iːn], with hollow– pronounced just like the word hollow in American English, listen here. This variant seems to be quite often confused with [ˈhɒləʊ’iːn], corresponding to the British pronunciation of hollow. However, according to the sources consulted, this is not an acceptable pronunciation of Halloween, and certainly not common in British English.