Planning for the weather is an important factor for making your trip to Lao Cai a success, especially when you're splurging. The hottest months are usually May and June, with an average temperature of 26°C, while the coldest months are January and December, with an average of 16°C. The rainiest months in Lao Cai are August, July, June and May, with each month seeing an average of 307 mm of rainfall.