In Yemen, the climate is tropical desert on the coast and in the lowlands, while it becomes mild and moderately rainy on the western plateau. During summer, from June to September, the southwest monsoon brings some rainfall on the western highlands, while in the rest of the country it brings widespread cloudiness but practically no rain.

The coast of the Red Sea (called Tihamah) has a desert climate, hot all year round, with highs around 28/30 °C (82/86 °F) in winter and 38/40 °C (100/104 °F) in summer. In summer, the humidity from the sea makes the heat sweltering. In Al Hudaydah, only 80 millimetres (3 inches) of rain per year fall. Despite the few rains, in this region, unhealthy and malarial areas are found, due to rivers that descend from the mountains and feed wetlands.
Here are the average temperatures of Al Hudaydah.
Average temperatures - Al Hudaydah

Al Hudaydah	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Al Hudaydah	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	18	18	21	24	26	28	29	27	26	23	20	19
Max (°C)	29	30	31	34	36	37	38	37	37	35	32	30
Min (°F)	64	64	70	75	79	82	84	81	79	73	68	66
Max (°F)	84	86	88	93	97	99	100	99	99	95	90	86

The sunshine amount, good all year round, decreases a bit in summer, due to the cloudiness brought by the southwest monsoon.
Sunshine - Al Hudaydah

Al Hudaydah	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Al Hudaydah	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	8	8	9	10	11	9	7	8	9	10	10	9

The Red Sea is warm enough for swimming all year round, and in summer it becomes very warm, as you can see in the following table.
Sea temperature - Al Hudaydah

Al Hudaydah	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Al Hudaydah	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	26	26	27	28	30	31	32	32	32	31	29	27
Sea (°F)	79	79	81	82	86	88	90	90	90	88	84	81

The islands of the Red Sea (Hanish, Kamaran, Perim) are desert as well, hot in winter and stifling in summer.

The coast of the Gulf of Aden has a similar climate, but during summer it's a bit less hot, especially in the central and eastern part, due to the southwest monsoon, which is felt more, and brings more often cloudy skies, as can be seen from the sunshine hours in Al Mukalla.
Sunshine - Al Mukalla

Al Mukalla	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Al Mukalla	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	9	9	9	10	11	9	5	6	8	10	10	10

However, the rains are still very scarce, even though in July and August there can be a drizzle that do not fall into the statistics (because in practice there is no accumulation). Here is the rainfall in Al Mukalla.
Average precipitation - Al Mukalla

Al Mukalla	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Al Mukalla	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	7	4	14	13	5	0	4	4	1	1	3	3	59
Prec.(in)	0.3	0.2	0.6	0.5	0.2	0	0.2	0.2	0	0	0.1	0.1	2.3
Days	1	1	2	2	1	0	1	1	0	0	0	0	9

In Aden, in the southern part of the coast, the daytime temperature in June and July is about 37 °C (99 °F), and in August and September it's about 36 °C (97 °F), while in Al Mukalla, more to the northeast and more exposed to the summer monsoon, it reaches "only" 33/34 °C (91/93 °F) in June and July, with a steady breeze and the sky often cloudy, even though the rains remain sporadic.
Average temperatures - Al Mukalla

Al Mukalla	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Al Mukalla	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	19	19	21	23	25	26	25	25	26	22	21	20
Max (°C)	27	27	29	31	32	34	33	32	32	31	30	28
Min (°F)	66	66	70	73	77	79	77	77	79	72	70	68
Max (°F)	81	81	84	88	90	93	91	90	90	88	86	82

The temperature of the sea in the Gulf of Aden is similar to that of the Red Sea, although in summer it warms up less, due to the wind and the cloudiness related to the monsoon.
Sea temperature - Al Mukalla

Al Mukalla	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Al Mukalla	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	26	26	27	28	30	31	30	29	30	29	27	26
Sea (°F)	79	79	81	82	86	88	86	84	86	84	81	79

The western plateau has a mild climate because of the high altitude, but also because it receives moderate rainfall from the summer monsoon. In Taiz, 760 mm (30 in) of rain per year fall, and in Ibb even 1,000 mm (40 in). The landscape is green in the south-west facing slopes, and with the terrace system, cultivation is possible even on declines. On the highest peaks, above 3,000 metres (9,800 ft), during winter sometimes it can snow.
The capital Sana'a is located at 2,200 metres (7,200 ft) above sea level, on the eastern side of the plateau, the one that receives less rainfall, and in particular it's protected by Jabal an Nabi Shu'ayb, the highest mountain in Yemen with its 3,666 metres (12,028 feet), however, here 240 mm (9.5 in) of rain per year fall, concentrated from July to September, with a maximum in August of 95 mm (3.7 in): precipitation is therefore typical of a semi-desert climate. A bit of rainfall may actually occur also in spring, from March to May, here as in the rest of the plateau. Here is the average precipitation.
Average precipitation - Sanaa

Sanaa	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Sanaa	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	1	9	7	35	13	3	45	95	30	1	1	1	241
Prec.(in)	0	0.4	0.3	1.4	0.5	0.1	1.8	3.7	1.2	0	0	0	9.5
Days	0	2	1	3	2	1	3	6	2	0	0	0	20

In Sana'a, winter is pleasantly warm and sunny during the day, with highs around 21/23 °C (70/73 °F) from November to February, but at night the temperature drops quite a bit, to around 10 °C (50 °F) and sometimes below. During summer the temperature is warm: the daily average is about 24 °C (75 °F); sometimes a few downpours or thunderstorms can occur.
Average temperatures - Sanaa

Sanaa	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Sanaa	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	10	12	15	16	18	19	20	19	18	13	10	10
Max (°C)	22	23	24	24	26	28	28	27	26	23	22	21
Min (°F)	50	54	59	61	64	66	68	66	64	55	50	50
Max (°F)	72	73	75	75	79	82	82	81	79	73	72	70

In Sana'a the sun shines all year round, but in July and August the hours of sunshine diminish a bit.
Sunshine - Sanaa

Sanaa	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Sanaa	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	8	8	9	9	10	9	6	7	9	10	10	9

The central-eastern part of Yemen (formerly South Yemen), is occupied by a coastal range, and in the interior by a plateau which declines from 1,000 to 400 metres (3,300 to 1,300 feet) from west to east, on the border with Oman; this is a desert area, although some rains in summer are possible along the coastal range. In the far north, along the border with Saudi Arabia, there is also a low altitude area occupied by the southern tip of the Rub 'al Khali, the sandy desert of southern Arabia. Here summer is very hot, with highs steadily above 40 °C (104 °F), but a bit of cloudiness linked to the summer monsoon can come to these parts too.
The island of Socotra, which is located between the Arabian Sea and the Indian Ocean, has a tropical desert climate: it's hot all year round, with daytime temperatures around 28/30 °C (82/86 °F) in winter, rising to 32/33 °C (90/91 °F) between April and June, and dropping again to 30 °C (86 °F) in summer, due to the monsoon.
Average temperatures - Socotra

Socotra	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Socotra	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	18	20	21	23	25	25	23	23	23	21	20	19
Max (°C)	28	29	30	32	33	32	30	29	30	31	30	28
Min (°F)	64	68	70	73	77	77	73	73	73	70	68	66
Max (°F)	82	84	86	90	91	90	86	84	86	88	86	82

In Socotra the rains are very scarce, at least in the lowlands, while the slopes of Mount Hajhir are greener, and host a xerophile vegetation, which is able to withstand the drought. However, from June to September, the island is affected by the cloudiness associated with the monsoon, it can receive a few showers, and is often windy. During winter, Socotra may experience some short showers, associated with the northeast Asian monsoon, which can collect some moisture when passing over the sea.
Here is the average precipitation.
Average precipitation - Socotra

Socotra	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Socotra	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	25	20	15	20	20	10	20	25	10	20	20	20	235
Prec.(in)	1	0.8	0.6	0.8	0.8	0.4	0.8	1	0.4	0.8	0.8	0.8	9.3
Days	2	2	2	3	4	6	10	9	5	3	3	3	52

In Socotra, the sky becomes often cloudy from mid-June to mid-September, while the sun shines in the rest of the year.
Sunshine - Socotra

Socotra	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Socotra	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	9	9	10	10	11	8	4	4	8	10	10	10

The Arabian Sea in Socotra is warm enough for swimming all year round as well, but in summer it's as warm as in winter, because of the wind brought by the monsoon, which lowers a bit the temperature; this also applies to the eastern coast of the mainland (see Al Ghaydan).
Sea temperature - Socotra

Socotra	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Socotra	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	26	26	27	29	30	28	26	25	26	27	27	26
Sea (°F)	79	79	81	84	86	82	79	77	79	81	81	79

Every now and then, Yemen can be reached by tropical cyclones, which bring strong winds and heavy rains (in desert areas, not able to absorb water, which can cause flash floods), as happened with Cyclone Chapala in early November 2015, and with Cyclone Megh in the following days, or with Deep Depression ARB 02 in October 2008, and the June 1996 cyclone. Cyclones form from May to December, and are more frequent at the beginning of the period (May-June), and at the end (October-December). The most affected areas are the island of Socotra, directly exposed in the open sea, and the central-eastern part of the coast, towards the border with Oman, which is hit more easily. Instead, the western part of the country is more protected, because once cyclones enter the Gulf of Aden, they tend to weaken.


The best months to visit Yemen as a whole, and also the island of Socotra, are January and February: along the coast and at lower altitudes it's a warm and sunny period; in the desert it's pleasant during the day, while it may become a bit cold at night, but at least you avoid the blistering heat of the long summer months. In December, the weather is usually good, but tropical cyclones are still possible, especially in the first half of the month.
In Sana'a and at high altitudes, winter is equally sunny, but it's mild during the day and a bit cold at night. Due to the mild temperatures, Sana'a can be visited all year round, but in summer, especially in July and August, it is often cloudy and some showers, at times heavy, can occur. Certain areas of the plateau are even more rainy and may experience flooding and landslides. The plateau can receive some showers also between March and May, however, wanting to visit only the plateau, in this area the best months are March-April and October-November, to avoid both the cold of winter nights and the summer rains. October is probably the best month.
As we have seen, the sea in Yemen is always warm enough for swimming, both in Socotra and along the coasts of the mainland.


In winter: for the plateau and Sana'a, spring/autumn clothes, light for the day, sun hat, sweater and jacket for the evening; for the mountain peaks, warm clothes, down jacket, sweater, gloves, hat; for the coast, summer clothes, a sweatshirt for the evening, snorkeling gear, water shoes or rubber soled shoes for the reef; for the desert, light clothes for the day, scarf or turban, desert boots or sandals, sweater or jacket for the evening and early morning.

In summer: for the plateau and Sana'a, light clothing, a sweatshirt for the evening, raincoat or umbrella; for the mountain tops, spring/autumn clothes for the day, sweatshirt and jacket, raincoat. For the desert and the Red Sea coast, lightweight clothes, made of natural fabric (cotton or linen), desert turban; for the coast of the Arabian Sea and Socotra, light clothes, light sweatshirt and scarf for the breeze, light raincoat.
For women, it is best to avoid shorts and miniskirts outside tourist clubs.