There are only two general seasons in Belize. Winter (Mild and relatively dry) and Summer (Warm and occasionally hot and humid. The official monsoon rainy season is June through August). Summers in San Pedro Town and the other Cayes strung out along the Barrier Reef are much milder than on the Belizean mainland, due to the proximity to the Sea and the cooling effects of the easterly trade winds and cloud cover which hold temperatures to the upper 80's and lower 90's during day time and mid to lower 80's nights.
The optimal location to live is literally on the edge of an upwind beach in a structure that encourages flow through ventilation, on the second or third floor. Off the beach, by a block or more, and one needs excellent mosquito proofing during the rainy season and good ventilation and/or air conditioning during Summer. Some folks with northern latitudinal origins find it more comfortable to have a small air conditioner in their bedrooms for sleeping comfort, no matter their location in Belize. Weather on the Cayes is usually quiet bearable year round. Inland is pretty hot and downright steamy during Summer.
Winters are a delight with their average 70's and very rare 60's when cold fronts push down from the north. Winters anywhere in Belize are a fact that attracts ever growing uncounted thousands of visitors during the (high) Tourist Season from mid-December through the end of May. The Caribbean Sea maintains an average 80 to 82 degrees water temperature year round which brings divers from the world over, to the famous Barrier Reef, on the eastern seaboard, especially in the winter.
For Belize in general, here is climate information:
The overall climate of Belize can be described as sub-tropical, with a brisk prevailing wind from the Caribbean Sea. The humidity while high, is seldom oppressive for long and is most noticeable along the coast. The mean annual humidity is 83%, but many days the humidity is masked by the cooling sea breezes.
Southeast tradewinds, averaging 10-13 knots, blow along the Belize coastal area and on the cayes most of the year, keeping temperatures pleasant even in the hottest months, except for a few weeks, generally around mid-August. They attain an uncanny consistency during the month of July.
Temperatures in Belize range from 50°F to 95°F with an annual mean of 79°F. Winter storms may bring the temperature down to the low 60's and it can reach the mid-90's on the mainland in the hottest part of summer. November to January are traditionally the coolest months with a 75°F average and May to September are the warmest at about a 81°F average. Location is a big factor for temperature as Cayo to the west can be several degrees colder then along the coast and during November at night, temperatures can fall to a beautiful 46°F in Cayo. In the mountains, the coldest days and nights might seem relatively very cold and blankets will definitely be needed at night. However, the mean annual temperatures on in the mountains is a perfectly comfortable 72°F.
There are definite wet and dry seasons. Rainfall is heaviest in the south and the jungle areas, lightest in the north and on the Cayes. The onset of the "dry" varies widely from year to year, but once the onset of the dry commences, the actual amount of rain falling during the "dry" is a predictable amount. This is not necessarily so for the remainder of the year though. As a general rule though, the higher the average rainfall, the greater are the departures from the norm. For example, rainfall in Punta Gorda to the south in September maybe 12 inches one year and 36 inches the following.
The number of rainy days varies considerable from place to place. The Cayo District has an average of 125 rainy days per year; Belize District averages about 171 rainy days, the Stann Creek District 183 days per year while in Punta Gorda they often have over 200 days of rain every year. Many of these rainy days are insignificant though, with early morning showers (called "night rain" by the locals" blossoming beautiful rainbows. These "night rains" are caused by cool air moving down from the mountains which cools the air along the cost causing a light rain.
Hurricanes occasionally occur; they are most likely to hit in September and October. Water temperature averages between 79 and 83 degrees F.
CLIMATE PATTERNS BY MONTH
The seasonal march of weather patterns in Belize is of considerable interests to vacationers and local farmers. While the following descriptions vary from year to year, once the pattern begins, the following weather conditions are usually predictable. Much of the following is taken from the classic book on Belizean Natural History by Charles Wright called "Land in British Honduras".
In January, the northeast tradewinds are normally established. In the Toledo District, except for a narrow coastal strip, the days are usually free from rain. On the upland Maya Mountains, the rainfall is only about 9 or 10 inches and almost all of the north of the country receives less then 3 inches of rain. In the south, the Mayan bean crops are maturing while in the north, the sugar cane harvesting is in full swing.
February is the most consistent month of the year in all districts except in Toledo. The dry easterly tradewinds blow steadily and the morning showers along the coast are gentle and infrequent. The Toledo coast gets about 6 inches of rain. Most of the northern part of the country gets only about an inch of rain. This is the month when you will see most of the clearing of forest by farmers throughout the country.
March is another reliable month. The pattern of rainfall is similar to February and the northern parts of the country often go all month without rain.. The steady trades are beginning to fluctuate a little and thunderstorms start to form over the Maya Mountains. Toledo has its first "dry" month of the year (averaging about 4 inches) and the eager Mayan farmers are beginning to burn their "Milpas" and sow their corn - though most will wait for April.
April ushers in the onset of the rains caused by the heating of the land. Huge thunderstorms begin to build over the hot Maya Mountains. The easterly trades are losing their force and the thunderstorms often move toward the coast. These afternoon buildups are beautiful to watch, with most of the lightening hitting deep within the Maya Mountains. Toledo has another dry month of only about 4 inches of rain, and the Mayan farmers wait till after the ground is soften by the rains to begin to plant their corn or burn the bush. In the north, the rainfall is very sporadic and go by the local name of "Iguana Rains".
During May, every part of the country can be assured of at least 2 inches of rain. The most striking characteristics of May are the majestic towering thunderheads. Strong convection currents caused by the heated land make these thunderheads daily occurrences.. By the end of the month, stormy conditions are becoming general throughout Belize and rainstorms are frequent in the south. The rainfall in Toledo may jump to 10 inches and storms blow in from the south east often lasting for three days.
During June, easterly winds become fairly strong and steady. Rainfall in Toledo rises to 24 inches average. The rains are fairly consistent throughout the country, though the coast may get more rain then the land immediately behind. The rains are warm and quick, with plenty of sunshine - perfect growing conditions for the vast tropical forests which cover the country. Most of the Mayan farmers stop farming operations as well as loggers. Even the north part of the country gets 7 or 8 inches of rain.
July closely mirrors June and the rainfall is similar. The extreme northern part of the country may receive a little less rain then June, but Toledo still gets about 24 inches of rain during the month. This rainfall is highly variable from year to year, but no part of the country receives less then 6 inches of rain during the month.
August sees the dying away of the southeasterly rains, and rainfall drops about 2 inches throughout the country. A dry westerly wind dominates the weather. Toledo still receives plenty of rain. These dry conditions around the country which may last for a couple of weeks are locally referred to as the "Little Dry". August is a fairly reliable month and westerly winds may become quite strong. The citrus harvest begins in the Stann Creek Valley with the sweetest juices you can imagine.
September is the month of dying breezes. North and west winds are light and variable. Most of the rains fall on the mountains where the warm moist sea breezes meet the cooling land mass at the close of the day. Evening and night rains are common. Toledo receives about 22 inches of rain and even the northern part of the country receives between 5 and 7 inches. Mayan farmers are harvesting their corn while planting early crops of beans.
In October, the "northers" increase. These northers bring in cold air from the north which meets the warm tropical air over Belize, causing rainfall and heavy northern winds. Strong "northers" blow right across the Maya Mountains and dump heavy rains on Toledo. Light "northers" drop heavy rains on the northern side of the Maya Mountains in the Cayo District. The northers can often be quite cool and cause light craft warnings throughout the country. They seldom last for more then 3 days at a time.
November sees the northerly winds at their most strongest and coldest. The east winds are very light and weak. Land breezes with cold air move down toward the coast where they meet the warm moist sea breeze increase rainfall along the barrier reef. There is a long rain shadow area extending for almost the entire length of the coastal plain along the foothills of the Maya Mountain Range. Grass fires in the savannas are common during the month of November within this rain shadow.
During December, the dry season should arrive and talk turns to the coming planting season. There is an increase in easterly winds and the northers are dying away. As the northers die, a slow moving belt of gentle rains move across the country and are known locally as the "mid-winter rains". The southeasterly trades begin to blow, carrying the cycle back into January.