Belize is situated on the Caribbean coast of Central America with Mexico to the North and Guatemala to the west and south. It lies between 15º45´ and 18º30´N and 87º30´ and 89º15´W. The terrain is low and flat along coastal areas and in some northern regions of the country while in the central and southern regions low mountains rise gradually to a height of 3,685 feet.
The climate of Belize is characterized by two seasons: a rainy and a dry season. In Belize, most of the year’s rainfall occurs during the period June to November, that is, the rainy season. It is noted from the graph below that the transition from dry to the rainy is very sharp. Mean annual rainfall across Belize ranges from 60 inches (1524mm) in the north to 160 inches (4064mm) in the south. Except for the southern regions, the rainfall is variable from year to year.
Figure 1 shows the distribution of average monthly rainfall data for Belize. The data are from stations in
(1) Southern Regions - Punta Gorda and TRDP (Toledo), Melinda (Stann Creek)
(2) Central Regions – Belmopan and Central Farm (Cayo)
(3) Northern Region - Consejo (Corozal) and Tower Hill (Orange Walk District).
The onset of the rainy season begins in the early May in Toledo, progressing north to the Stann Creek, Belize, Cayo and Orange Walk District in late May, followed by Corozal District in early June. The onset was determined by the first occurrence after the1st of May in which there was more than an inch of rainfall in seven days with at least four days receiving some rainfall.
In the south the rainfall is further enhanced by the intrusion of the Inter-Tropical Convergence Zone (ITCZ) as it journeys northwards. Orographic lifting over steep slopes in the south also enhances rainfall activity. The southern region has one maximum which occurs in the month of July and is by far the wettest month.
Central Regions show a primary and secondary maxima occurring in June and September. Each of these is significantly less than the single maximum for the south.
The data for the Northern region show that rainfall is more evenly distributed during the same period with no significant variation as in the other regions.
The rainy season exhibits a break or mark decrease in the month of August. This break is known as the "Mauga" season. However, this pattern is not evident in the Toledo district.
The main synoptic features that produce on the rainfall are Tropical waves, Tropical storms and Hurricanes which moves westward through the Caribbean from June to November. Tropical waves can be active or inactive systems and peak activity occurs during the months of June and July. Tropical storms and hurricanes peak during the months of September and October even though they vary in number from year to year. Figure 2 shows that most of the tropical storms and hurricanes frequent the area during the month of September.
In addition there are cold fronts that progress southeastward from the Continental USA into the Northwest Caribbean. The effect of frontal activity on rainfall distribution and therefore climatic conditions begins in October and ends in April peaking through December and January. A cold front moves across Belize about once every 10 days.
Other features include upper level troughs and cold core lows to lesser degrees; these sometimes interact with surface low level troughs resulting in the enhancement of precipitation. Below is a table showing the frequency of the synoptic systems that affect Belize.
The transition from wet to dry is a gradual process. The dry season is from November to May with April as the driest month. The dry season can be subdivided into a cool transition from November to February, as a result of the incursion of frontal systems and a warm dry period from March to May when high pressure systems in the Atlantic produce stable and windy south easterlies.
Upper level troughs show no preferential time of occurrence. Although cold fronts affect the country from October through to April the most likely months for frontal passages are December, January and February (Figure 4). In December and January fronts are most likely to become stationary over Belize. Surface troughs show a modal frequency in November with secondary maxima in December. Cold core lows frequently occur in the months of July, August and September. Those not of the cold core variety are found most frequently in July and August.
The mean temperature varies from 81°F/ 27°C along the coast to 69°F/21°C in the hills. The coldest month is January while the highest temperatures are experienced during the month of May.