Map from Google - Turkmenistan

In Turkmenistan, a country of Central Asia, the climate is arid continental, with cold winters and hot summers. Being subject to different air masses, the weather is unstable and there can be cold spells as well as heatwaves. Even the wind can be strong, raising dust storms.
Much of Turkmenistan is occupied by the Karakum Desert, where in summer the temperature can reach as high as 50 °C (122 °F). Even the coasts of the Caspian Sea are desert, but they are milder in winter, while in summer they are a bit less hot, but more humid. In the north, in the area once occupied by the Aral Sea, we find Lake Sarygamysh, fed by a branch of the Amu Darya River, and once part of the same Aral Sea.
Winter is cold in the north, while it becomes milder in the centre and south: the average temperature in January drops below freezing (0 °C or 32 °F) in the north, while in the south it rises to around 5/6 °C (41/43 °F). Due to the aridity of the climate, snowfalls may occur, but they are generally not abundant. Summer is hot everywhere: the daily average temperature in July is around 27/28 °C (81/82 °F) in the north and on the shores of the Caspian Sea, while it can even exceed 30 °C (86 °F) in the centre and south. The mildest area of the country is the south-west, which is less cold in winter, and less hot but more humid in summer, because of the swampy areas that are found there, as well as of the waters of the Caspian Sea.
In the south, we find some mountain ranges, such as Kopet Dag (or Turkmen-Khorasan), from whose slopes hot winds can descend, leading to rapid increases in temperature. Another mountain range, Köýtendag (or Kugitangtau), lies in the east, and reaches its highest point in Mount Aýrybaba, 3,138 metres (10,295 feet) high, which is the highest mountain of the country. On the other hand, to the north there are no obstacles, so cold air masses of Siberian origin can easily reach the country, from April to October, but more likely from November to March.
The capital Ashgabat is located in the south, at the foothills of the Kopet Dag, from which strong down-slope winds, warm and dry, can blow all year round. Although these mountains are around 3,000 metres (10,000 ft) high, they are almost always devoid of snow, due to the aridity of the climate. In Ashgabat, precipitation amounts to 220 millimetres (8.5 inches) per year, so we are at desert-like levels, but it's still more than in other areas, due to the proximity to the mountains; the rainiest seasons are winter and spring.
Here is the average precipitation.
Average precipitation - Ashgabat
AshgabatJanFebMarAprMayJunJulAugSepOctNovDecYear
AshgabatJFMAMJJASONDY
Prec. (mm)25204540306213101520218
Prec.(in)10.81.81.61.20.20.100.10.40.60.88.6
Days77874211134752

Winter is a bit cold but not freezing: the average in January is 3 °C (37.5 °F), and for long periods the temperature can be acceptable. The southern wind can raise the temperature to around 20/25 °C (68/77 °F) even in winter. On the other hand, sometimes cold air masses from Siberia can cause waves of frost, with lows around -10/-15 °C (5/14 °F). Summer, from June to August, is torrid, with highs around 37/38 °C (99/100 °F), but with peaks of 45 °C (113 °F).
Here are the average temperatures of Ashgabat.
Average temperatures - Ashgabat
AshgabatJanFebMarAprMayJunJulAugSepOctNovDec
AshgabatJFMAMJJASOND
Min (°C)-205111621232115951
Max (°C)71016243036383732231710
Min (°F)283241526170737059484134
Max (°F)4550617586971009990736350

Ashgabat

Turkmenbashy (formerly Krasnovodsk), is located further north, on the coast of the Caspian Sea, but it's tempered by the waters of the great salt lake, therefore has a similar climate: the average in January is 3.5 °C (38.5 °F), but even this city is not free from cold waves in winter; the average in July is 28.5 °C (83.5 °F), with highs around 35 °C (95 °F), but with peaks of 45 °C (113 °F).
Average temperatures - Turkmenbashy
TurkmenbashyJanFebMarAprMayJunJulAugSepOctNovDec
TurkmenbashyJFMAMJJASOND
Min (°C)003914192222171051
Max (°C)891320263235352922149
Min (°F)323237485766727263504134
Max (°F)464855687990959584725748

In Turkmenbashy, the annual precipitation, 125 mm (4.9 in), is typical of a desert climate. Here is the average precipitation.
Average precipitation - Turkmenbashy
TurkmenbashyJanFebMarAprMayJunJulAugSepOctNovDecYear
TurkmenbashyJFMAMJJASONDY
Prec. (mm)1213171693255111913125
Prec.(in)0.50.50.70.60.40.10.10.20.20.40.70.54.9
Days54543111123535

In the far north, in Dashoguz (ex Tashauz), the January average drops to -3.5 °C (25.5 °F), while in July it's 28 °C (82 °F). Summer is therefore still hot, while winter is much colder, and waves of frost are more frequent, when lows can drop to around -20/-25 °C (-13/-4 °F). Precipitation is still very low, around 100 mm (4 in) per year. Here are the average temperatures.
Average temperatures - Dashoguz
DashoguzJanFebMarAprMayJunJulAugSepOctNovDec
DashoguzJFMAMJJASOND
Min (°C)-8-708141921181250-5
Max (°C)141121293436332719103
Min (°F)181932465766706454413223
Max (°F)343952708493979181665037

When to go

The best times to visit Turkmenistan are spring and autumn, to avoid the extreme temperatures typical of the country, and in particular the months of April and October, bearing in mind that in any case it can get cold at night, especially in the north, and hot during the day, especially in the south. In the capital and in the south, where the hot summer is longer, you can choose the periods from mid-March to mid-April and from mid-October to mid-November.

What to pack

In winter: in Ashgabat and central and southern main cities, warm clothing, sweater, down jacket, scarf for the wind, being ready to remove the outer layer in mild days, but also to wear warmer clothes during cold waves, therefore with parka, fur hat, scarf, gloves. In the far north, in Dashoguz and Lake Sarygamysh, very warm clothes are almost always necessary.
In summer: lightweight clothes, loose-fitting and made of natural fabric (cotton or linen), sun hat, desert turban, a sweatshirt for the evening, a light sweatshirt for the breeze on the Caspian Sea shores. For the mountains, light clothes for the day, sun hat, sweatshirt and light jacket for the evening, hiking shoes; for the summit of Aýrybaba, sweater and jacket for the evening.
For women, it is best to avoid shorts and miniskirts.