Qatar sits in the Arabian Desert, and its climate is shaped by that fact. Summer is extreme; winter is genuinely pleasant.
October to April is the time to go. Temperatures range from around 15°C overnight to the mid-20s in the day in December and January, rising to low 30s by March and April. Evenings in winter can be surprisingly chilly. This is when outdoor life happens — desert trips, coastal walks, the beach. Most cultural events, sports fixtures, and festivals are scheduled in these months.
May through September is hot in ways that reshape daily life. Temperatures regularly exceed 40°C and routinely touch 45°C, with high humidity making it feel worse. Being outside for any length of time during the middle of the day is genuinely dangerous. Everything moves indoors. If you visit in summer, you will spend most of your time in air-conditioned malls, hotels, and museums, which is fine if that is what you want.
Ramadan moves through the calendar year by year (as an Islamic lunar month). During Ramadan, daytime eating and drinking in public is prohibited, many restaurants only open after sunset, and the pace of the city changes. Non-Muslim visitors are welcome, but need to be respectful. The evenings of Ramadan — when the fast breaks at Iftar — are lively and worth experiencing if you are around.
The FIFA World Cup was held in November–December 2022, an unusual schedule chosen specifically to avoid summer heat. Qatar got to use all eight stadiums in agreeable weather, and the infrastructure legacy remains.