The weather in Malaysia is characterised by two monsoon regimes, namely, the Southwest Monsoon from late May to September, and the Northeast Monsoon from November to March. The Northeast Monsoon brings heavy rainfall, particularly to the east coast states of Peninsular Malaysia and western Sarawak, whereas the Southwest Monsoon normally signifies relatively drier weather. Monsoon does not mean rain, it is the name of the prevailing winds, but it does mean heavy rain can be expected during monsoon season.

What is called "heavy rain" in Malaysia, more often than not, could qualify as a storm in other parts of the world, but because the rains come almost daily in the monsoon season, Malaysians handle the falling of whole trees, immense flooding and electrical blackouts with nonchalance. Buildings in Malaysia are built to withstand the worst of the storms, so what city folk like to do during a storm is to avoid the traffic jam (due to poor visibility) and hit the shopping malls.

For the rest of the year, occasional light showers may occur. Year round, it is mostly between 25 to 32 deg C. You have come to the right place if you're looking for warmth. Apply water-resistant, sweat-resistant sunblock if you are going outdoors and bring more with you to reapply. Though it may be cloudy or even rainy, UVA rays penetrate the clouds and rain to reach the skin. Sunglasses and summer hat are recommended at the beach. Kuala Lumpur is also very humid, almost 90%.

When to come to Malaysia is a matter of preference. Some love the excitement of the monsoon season weather. Terengganu holds a Monsoon Cup during the Northeast Monsoon for adventurous yacht men to challenge themselves at. Some would find the daily storms an interference in the many outdoor activities available in Malaysia, such as jungle trekking. Furthermore, different states are affected differently by the different monsoon seasons. For example, Kelantan and Terengganu are flooded annually by the Northeast Monsoon, but barely notice the Southwest Monsoon.

During July to October Indonesia is clearing large areas of forest by fire on an industrial level, and the heavy smoke is blown throughout the south-east asian region. The haze generally coincides with the dry season, when there is no rain to kill the fire and settle the smoke, so it can build up to an unpleasant level of pollution at some point between July and October. This pollution can last between 2 weeks to 2 months (the record-length was in 2015).  At the best it is not noticeable, at worse it gives a heavy dense fog with a little visibility and is dangerous to heath.  The impact will solely depend on the areas being burnt and the direction of the prevailing winds and weather patterns.

Otherwise, the best way to decide when to come to Malaysia is to consider the timing of various events to be held. Look for an annual event calendar from the Tourist Board, or other sources, and research the various festivals or events held in that year. August, the month of Malaysia's Independence Day provides great sales for shopaholics and cool parties and concerts for club-hoppers and party-goers. Ramadhan Month is a nice month for food-loving non-Muslims to visit, because during the day, none of the attractions are crowded as the majority of people are fasting and praying, and as the sun sets, the most decadent amount and variety of food spills out from the restaurants all over Malaysia, never seen at any other time of the year. Different states have different events, too, depending on the time of the year. Sepang has the F1 race, Penang has dragon boat racing, Langkawi has the yacht regatta. By no means is this an exhaustive list, because new events are organized all the time.

In the end, no matter when you come to Malaysia, it will be hot and humid; you may see some rain, but the sun will shine. You can be assured of delicious food being always widely available and something to do no matter the weather or the time of year.