Map from Google - Venezuela

In Venezuela the climate is hot all year round, at least at low altitudes, so the main differences are found in the seasonal rain pattern: there is a dry season (which usually runs from mid-December to mid-April) and a rainy season (usually, from late April to mid-November). The rainy season is also the most sultry and unpleasant
However, the vastness of the territory and the presence of mountain ranges and plateaus complicate things, making the climate more or less rainy depending on area, and more or less warm depending on altitude. Venezuela is located just north of the Equator, so temperature fluctuations over the seasons are limited, although the dry season is typically the coolest one, albeit slightly.

In the northern coast, there are significant differences in rainfall: the eastern part is quite rainy, so much so that the huge Orinoco Delta is covered with mangroves and rainforests. Here, about 2,000 millimetres (80 inches) of rain per year fall, and there is not a real dry season, however, the least rainy period is February-March.
Proceeding west, precipitation drops to around 1,000 mm (40 in) per year, or even below, as happens in Guiria, where it's about 900 mm (35.5 in), and the period from January to May is quite dry.
Further to the west, in Barcelona, only 650 mm (25.6 in) of rain per year fall, and the rainy season runs from June to September, while it rains very little from December to April.
Here is the average precipitation in Barcelona.
Average precipitation - Barcelona
BarcelonaJanFebMarAprMayJunJulAugSepOctNovDecYear
BarcelonaJFMAMJJASONDY
Prec. (mm)104674510013511075655025632
Prec.(in)0.40.20.20.31.83.95.34.332.62124.9
Days111141214131076373

Here are the mean temperatures of Barcelona.
Average temperatures - Barcelona
BarcelonaJanFebMarAprMayJunJulAugSepOctNovDec
BarcelonaJFMAMJJASOND
Min (°C)202021222322212121222120
Max (°C)313132333332313132323231
Min (°F)686870727372707070727068
Max (°F)888890919190888890909088

The islands of the Caribbean Sea (Isla Margarita, Los Roques, La Orchila, La Blanquilla, Los Hermanos, Los Testigos, La Tortuga) are arid, since the annual precipitation amount is usually around 500 mm (20 in), and sometimes even below. Here the rainy season is not so noticeable, because in the summer months the prevailing winds, the southeast trade winds, blow from the mainland, and in fact the islands are part of the so-called Leeward Antilles. However, from November to mid-February, some additional showers may occur, due to the northeast trade winds, which blow in this period.
In the western part, the coast bordering the Gulf of Venezuela (see Maracaibo, Coro), is usually sheltered from the northeast trade winds. In the short stretch of coast belonging to the Guajira Peninsula, we find the Venezuelan side of the Guajira desert, where less than 300 millimetres (12 inches) of rain per year fall. North of Coro, and south of the isthmus connecting the mainland with the Paraguaná Peninsula, we find the national park of Medanos de Coro, where there is a small sand desert, with towering dunes as high as 40 metres (130 feet).
In Maracaibo from December to April it almost never rains, and usually the rains are not abundant even in the period from May to October, excluding October, when rainfall reaches 150 mm (6 in). However, the rains are irregular from year to year, and sometimes they can be plentiful, although there is a break in the rains in July, which is almost always respected.
Here is the average precipitation.
Average precipitation - Maracaibo
MaracaiboJanFebMarAprMayJunJulAugSepOctNovDecYear
MaracaiboJFMAMJJASONDY
Prec. (mm)2182070554555701508515576
Prec.(in)0.100.30.82.82.21.82.22.85.93.30.622.7
Days00125456866144

In Maracaibo it's hot all year round. From May to October, temperatures are slightly higher, while January and February (and also the Christmas period) are the least hot months (or better, the least sultry and therefore the most pleasant), as well as the sunniest.
Average temperatures - Maracaibo
MaracaiboJanFebMarAprMayJunJulAugSepOctNovDec
MaracaiboJFMAMJJASOND
Min (°C)232323242525252525242424
Max (°C)323233333334343434333333
Min (°F)737373757777777777757575
Max (°F)909091919193939393919191

For swimming, the Caribbean sea is warm all year round, as you can see from the water temperatures at Maracaibo.
Sea temperature - Maracaibo
MaracaiboJanFebMarAprMayJunJulAugSepOctNovDec
MaracaiboJFMAMJJASOND
Sea (°C)262526262727272828292827
Sea (°F)797779798181818282848281

Isla Margarita

The northernmost part of Venezuela, namely the Paraguanà Peninsula, the Paria Peninsula and the islands, is located in the southern end of the trajectory of hurricanes, which means that it can sometimes be affected by tropical cyclones, more or less intense. The season in which hurricanes form, runs from June to November, but the phenomenon is more likely between August and October. For example, these areas were affected by Hurricane 2 (or Trinidad hurricane) in July 1933, Tropical Storm Alma in August 1974, and were touched by Hurricane Ivan in September 2004, which more passed to the north.

The capital Caracas is located in a valley, about 15 km (9 miles) away from the sea; however, the city is isolated from the sea by the mountain range called Cordillera de la Costa Central, in the part of the range where the Ávila National Park is found; moreover its altitude, about 900 metres (3,000 feet) is sufficient to temper the heat, making the climate pleasant throughout the year, so that the temperatures are around 24/27 °C (75/81 °F) during the day, and 13/17 °C (55/63 °F) at night. In fact, around this altitude the so-called tierras templadas (temperate lands) begin. The coolest period is from December to March, when at night the temperature can drop to 10 °C (50 °F). From May to December, the rains are quite frequent, however, they occur in the form of showers and thunderstorms, which do not last long and soon leave space for the sun. The period from January to mid-April is the driest, and sees very little rainfall. The total annual precipitation is about 835 mm (33 in).
Here is the average precipitation.
Average precipitation - Caracas
CaracasJanFebMarAprMayJunJulAugSepOctNovDecYear
CaracasJFMAMJJASONDY
Prec. (mm)20101533801001101101051109545833
Prec.(in)0.80.40.61.33.13.94.34.34.14.33.71.832.8
Days522281313131211118100

From December to February, fog may appear in the coolest hours. Sometimes, especially from March to September, the down-slope wind coming from the ranges of El Ávila and Naiguatá, can lead to sudden increases in temperature, and bring a bit of torrid heat.
Average temperatures - Caracas
CaracasJanFebMarAprMayJunJulAugSepOctNovDec
CaracasJFMAMJJASOND
Min (°C)131314161717171616161614
Max (°C)242526262726262627262526
Min (°F)555557616363636161616157
Max (°F)757779798179797981797779

In addition to the capital, in Venezuela there are other cities located at high elevations, and whose climate is tempered by altitude. Barquisimeto is located at 600 metres (2,000 feet), so the temperature is a bit higher than in Caracas: around 28/29 °C (82/84 °F) during the day, and 20/21 °C (68/70 °F) at night. The city is located in the north-western arid region, in fact it receives only 540 mm (21.2 in) of rain per year, which is also quite irregular, but most abundant from April to July.
On the contrary, Mérida is located at a higher altitude, 1,500 metres (5,000 feet), so it has a cooler climate, with average highs around 23/25 °C (73/77 °F). Here are the average temperatures.
Average temperatures - Mérida
MéridaJanFebMarAprMayJunJulAugSepOctNovDec
MéridaJFMAMJJASOND
Min (°C)151516171717161717161615
Max (°C)232324242424252525242423
Min (°F)595961636363616363616159
Max (°F)737375757575777777757573

The city is located in the south-west, in a valley, and a short distance from the highest mountain in Venezuela, Pico Bolìvar, towering with its 4,978 metres (16,332 feet). Here the rains are plentiful: 1,700 mm (67 in) per year, with a very rainy period from April to November, and a fairly dry period from January to March.
Here is the average precipitation.
Average precipitation - Mérida
MéridaJanFebMarAprMayJunJulAugSepOctNovDecYear
MéridaJFMAMJJASONDY
Prec. (mm)405050170230160130140190260190801690
Prec.(in)1.6226.79.16.35.15.57.510.27.53.166.5
Days8811162016181819191610179

Mérida cable car

South of Caracas, there is a large flat area (called El Llano or Los llanos as plural), very interesting from the point of view of wildlife, and covered by savanna (especially in the states of Apure and Guarico). From the point of view of the climate, this region is characterized by a sharp alternation between a dry and a rainy season. In this area there are some national parks, such as Aguaro-Guariquito and Santos Luzardo.
The city of San Fernando is located in this area. Lying in the plain, it is hot all year round, but due to the distance from the sea, in the last part of the dry season (which runs from mid-November to mid April), and before the rainy season (therefore, in March and April), temperatures reach considerable values: 35/36 °C (95/97 °F) in March and April are the norm. But then the rains come, definitely intense from June to mid-September, and the temperature returns to tropical values, around 29/30 °C (84/86 °F), in addition to moisture, which becomes high.
Here is the average precipitation.
Average precipitation - San Fernando
San FernandoJanFebMarAprMayJunJulAugSepOctNovDecYear
San FernandoJFMAMJJASONDY
Prec. (mm)14147018528030528017013040111490
Prec.(in)00.20.62.87.31112116.75.11.60.458.7
Days011412192420151042112

Rainfall amounts to 1,500 mm (60 in) per year, but the dry season is too long to allow the forest to grow here. To visit this area, the best time is December-January, which, however, is hot, because from February to April it becomes even hotter. Here are the average temperatures.
Average temperatures - San Fernando
San FernandoJanFebMarAprMayJunJulAugSepOctNovDec
San FernandoJFMAMJJASOND
Min (°C)222222232322222223222222
Max (°C)323336353231303031323232
Min (°F)727272737372727273727272
Max (°F)909197959088868688909090

Aguaro-Guariquito

To the east, the area of Ciudad Bolìvar and El Tigre (ie the southern part of the states of Anzoategui and Monagas, and the north of Bolìvar) has an even more arid landscape, since precipitation is lower than 1,000 mm (40 in) per year, though the rainfall pattern is similar, with a rainy season from May to October.
Another area covered by the savanna, is located in the south-east, in the plateau called Gran Sabana, on the border with Guyana and Brazil. This plateau is part of the larger Guiana Shield. In this area, there are also mountain peaks such as Mount Roraima and Kukenan Tepui.
In Santa Elena, at 900 metres (3,000 feet) above sea level, the heat is less intense than in the plains, being tempered by altitude. Here are the average temperatures.
Average temperatures - Santa Elena
Santa ElenaJanFebMarAprMayJunJulAugSepOctNovDec
Santa ElenaJFMAMJJASOND
Min (°C)161718181818171717171717
Max (°C)303131302928282829293029
Min (°F)616364646464636363636363
Max (°F)868888868482828284848684

In Santa Elena the rains are quite abundant, amounting to 1,600 mm (63 in) per year. The driest months are January and February, while the wettest period is from May to August. Here is the average precipitation.
Average precipitation - Santa Elena
Santa ElenaJanFebMarAprMayJunJulAugSepOctNovDecYear
Santa ElenaJFMAMJJASONDY
Prec. (mm)50609513521525021517095901301201625
Prec.(in)22.43.75.38.59.88.56.73.73.55.14.764
Days10911162324242215121414194

Further to the west, but still in the state of Bolìvar, we find the huge Canaima National Park, which is generally more humid and has greener landscapes; here we find incredible waterfalls such as Salto Angel, 979 metres (3,211 feet) high, and Salto Kukenan, 674 metres (2,211 feet) high.

Salto Angel

In eastern and southern Venezuela, from the Orinoco Delta to the southern state of Amazonas (with the exception of the aforementioned Gran Sabana), where the Venezuelan side of the Amazon is found, the climate is so rainy as to give life to rainforests. Rainfall exceeds 2,000 mm (80 in) per year, and the relatively dry season (in which, however, the rains are not so rare) is from December to March.

As we have already said, in Venezuela the are also high mountains, especially in the west, where there is a small portion of the Andes (the Cordillera de Mérida). In the aforementioned Pico Bolìvar, at almost 5,000 metres (16,400 ft) above sea level, there are three small glaciers. In fact, we find an average temperature around freezing at 5,000 metres (16,400 ft); as we have seen, since the country lies at the Equator, temperatures are quite constant throughout the year. Usually, it gets cold above 3,000 metres (9,800 ft).

When to go

Apart from the individual regions, of which the climate has been explained in detail, wanting to find the best time to visit all of Venezuela, you can choose January and February, also including the Christmas period at the end of December.
More generally, the dry period, or in any case the least rainy (mid-December to mid-April) is preferable to the rainy season (from late April to mid-November).

What to pack

For the plain, in general, light clothing all year round. For the forest, tropics-friendly, loose fitting clothing, light shirts and pants of natural fibres (cotton, linen) or synthetics that breathe, maybe with long sleeves for mosquitoes; a light sweater and a light raincoat for thunderstorms, even in the savanna during the rainy season. For the coasts, although it's always hot, you can bring a light sweatshirt for the breeze, especially from December to February.
For Caracas, Mérida, and tierras templadas, light clothing, a sweater for the evening, a jacket for the evening especially from December to March; raincoat or umbrella from May to December in Caracas, and throughout the year in Mérida, but especially from April to November.
For the high mountains, warm clothes, down jacket, hat, gloves, scarf, hiking shoes.