Daytime temperatures usually reach 24°C in Key West in January, falling to 17°C at night. The weather is pleasant, with a multitude of outdoor activities at disposal. January is a delightful month in the mild winter of Key West when the average temperatures are in a comfortable range of 65°F (18.3°C) to 75°F (23.9°C). Get the monthly weather forecast for Key West, FL, including daily high/low, historical averages, to help you plan ahead. You can view the weather statistics for all the month, but also by using the tabs for the beginning, the middle and the end of the month. The average surface water temperature in Key West is essentially constant during January, remaining within 1°F of 74°F throughout. Rain is not a showstopper in the dry season. Average values and totals based on weather data of recent years: Weather by month, temperatures and climate table in January for Key West Key West: Climatic table and weather throughout the year. Winter is usually devoid of extremely low temperatures. This section reports on the wide-area average surface temperature of that water. Daytime maximum temperatures average around a muggy 24°C (75°F), whilst at night 17°C (63°F) is normal. January is in the winter in Key West and is typically the coldest month of the year. Key West is located near a large body of water (e.g., ocean, sea, or large lake). Daytime maximum temperatures average around a muggy 24°C (75°F), whilst at night 17°C (63°F) is normal. The weather in Key West in the month of january comes from statistical datas on the last years. The average sea surface temperature in January 2020 for Key West was 77.1°F.The maximum and minimum values were 73.8°F and 80.4°F respectively. Weather in Key West in january 2021.