Valparaíso weather in December

December is summer here and the board describes it as one long dry day with a cold end: around 30C in the afternoon, low twenties by ten at night, cooler again before dawn. Our row is that swing written as two numbers, 30C over 11.6C - an eighteen-degree range inside a single date. At 53.6 percent humidity the heat is dry, so a step into the shade cools you immediately, but the sun is strong enough that finding shade is the whole trick. Rain is 6.5mm across not quite one day. Most evenings want a sweater, and hotels are air conditioned where apartments often are not. The smog the board argues about belongs to winter: AQI 75 here against 138 in July. The record: 13.1 hours of sun.

Forum posters describe August across central Chile's Santiago/Viña del Mar corridor as cold and rainy, with Santiago itself seeing lows around 0-5C and highs 12-22C - conditions that grow milder heading north and colder, wetter heading south. Valparaiso's own coastal setting, right on the Pacific, tends to run a touch milder and less extreme day-to-day than inland Santiago, without Santiago's sharper temperature swings between a cold morning and a much warmer afternoon. Posters note this is genuinely winter in Chile, so beach weather is off the table at either Valparaiso or nearby Viña. Posters do flag a real upside: August draws noticeably fewer crowds than the summer season, appealing to travelers who prefer a quieter visit. Posters generally rate August as cold, damp and distinctly winter for Valparaiso, but with real crowd-avoidance appeal for those prepared for the weather.

February is peak Chilean holiday season and the coast is crowded for it — mid-February is the high point of the high season, and the forum's advice is to book lodging and flights as early as you can. The weather note that matters is the contrast: while Santiago is blazing hot and half-emptied out in February, Valparaíso stays coastal and moderate, averaging only about 19°C by day and 15 overnight, with no rain at all across the month. The sea is cooler still, near 17°C. Bring a layer for the evening — this is not a hot beach summer, it is a mild one.