January
January is the coolest month of the year with the average maximum temperature
around 24°C and an average minimum of 14°C. However, records show that
temperatures have been reported as high as 32°C and as low as 8°C during the
month. It is often cloudy and unsettled as mid-latitude weather disturbances
penetrate into the Gulf bringing changeable weather and cool, winter Shamals in
their wake. Such Shamals that sweep down the Gulf frequently produce intense
convective activity resulting in squally, thundery weather with showers, storms
and high seas. On average five or six rain days can be expected during the
month, however as many as seventeen rain days have been recorded. Rainfall is
often short lived and intense with isolated thunderstorms producing the
majority of the recorded rain. Large fluctuations in rainfall occur from year
to year with occasional dry years or with as much as 108.8 mm falling during
the month. On clear fine days the weather is pleasant and warm with weak
afternoon sea breezes. Sea temperatures are around 21°C.
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February
Temperatures increase a degree or so in February with mean maximums typically
around 25 °C, however the extreme maximum temperature has reached 36°C with a
minimum as low as 7°C. Unsettled wintry weather is more frequent, winter
Shamals persist with the associated unsettled weather and strong winds. This
makes February one of the windiest months with regular Shamals affecting the
Gulf. Shamals bring cool, windy and occasionally showery conditions to the
southern Gulf. Ahead of an approaching shamal strong Southeasterly winds often
develop bringing hot, dry conditions and occasional sandstorms. The transition
from Southeasterly winds ahead of the trough to the Northwesterly Shamal is
therefore usually associated with a marked fall in temperature. February is the
wettest month of the year, with an average of 25mm of rain, it also holds the
record for the most rainfall in a day, 150.2 mm in 1988 at Dubai Airport. The
expected number of rain days during the month is 5 but has been as high as 12.
The relatively warm, moist air over the Gulf combined with winter weather
patterns helps to fuel cloud and storm development. Local convergence and the
effect of the mountains in the east of the country also act to generate or
enhance rainfall.
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March
The
period March through to May are the "Spring" months in Dubai when the
temperature begins its steady climb towards the summer peaks. Average maximum
temperatures rise to around 28°C in March however winter weather patterns
continue to affect the area. This combination means that a more abundant supply
of energy is available for the development of cloud and storms should the
correct combination of meteorological features exist. March is therefore often
a very changeable month when Dubai can experience a wide range of weather
phenomena. This is why March has the highest expected number of rain days, six
on average and up to eighteen in the past as well as the most frequent
occurrence of thunderstorms. Average rainfall for the month is 21mm but has
been as high as 155 mm. As in February, in between the periods of unsettled
weather, winds tend to veer to the Southeast and bring warm, dry desert air to
the coast. Temperatures have been recorded in the low 40’s °C later in the
month however extreme minimum’s of 11°C have also been recorded.
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April
As the sun begins to climb in the sky, April brings some beautiful weather to
the Emirates. Maximum temperatures are typically around 33°C, humidity is
generally low and although winter systems are still possible they are becoming
a lot less frequent. Expected rainfall is down to around 7 mm falling on three
days during the month but in exceptional years rainfall has been as high as 60
mm. The coastal, afternoon sea breeze increases in strength as the temperature
gradient between the land and the sea develops. The increase in temperature
does however mean that the occasional storms that do develop can be violent
with heavy rain and squalls. One particularly violent storm in 1981 produced
golf ball sized hail stones and in 2003 a storm and squall produced mean winds
of 53 kts gusting to 71 kts. As the month progresses, the high level Jet stream
starts to move northwards, cutting off southward incursions of unsettled
weather and cool Northwesterly winds to the region. The sea in coastal waters
continues to warm up with a mean temperature for the month of about 25°C.
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May
May often marks the beginning of the summer heat, average maximum temperatures
are between 37 and 38°C, but extremes highs of 47°C have been recorded. The
Humidity is however at its lowest level for the year and rain and thunderstorms
are extremely rare in coastal areas. Hot, dry Southeasterly winds often prevail
in May but comfort levels remain reasonable because of the low humidity. Sea
temperatures increase to around 28 to 29 °C.
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June
During June,low pressure over Southern Iran, which develops in the lee of the
mountains, combines with a ridge of high pressure over Saudi Arabia to produce
a Northwesterly gradient which can persist over the Gulf for up to six weeks.
The phenomena is known locally as the “Forty day Shamal”. From year to year the
onset and strength of this effect can vary widely. Hot and generally dry
conditions prevail throughout the month with periods of Southeasterly winds
replacing the Northwesterly flow when the lee low weakens. When the winds are
from the Northwest they bring hot and sometimes dusty conditions from the
deserts of Saudi Arabia, Kuwait and Iraq. Temperatures typically reach a
maximum of around 39°C but can be as high as 47°C, low humidity at this time
helps to keep stress levels reasonably low. Rainfall is infrequent during June
with most coastal stations having a completely dry month. Over the mountains in
the East of the Emirate summer storms do develop and can cause intense
localised heavy rainstorms and flash flooding in the wadi’s . Dry squalls from
these storms do occasionally reach the coast dramatically reducing the
visibility for a few hours. Sea temperatures increase into the low 30’s°C.
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July
As the summer advances and the monsoon spreads northwards over India the lee
low effect over southern Iran begins to weaken and pressure gradients become
weak over the area. Land and sea breezes begin to dominate the flow and as the
sea is still warming up thermal gradients can be strong with a moderate to
fresh Northwesterly sea breeze most afternoons. The humidity can become
extremely high at times producing severe stress. The combination of high
temperatures and high humidity can make atmospheric conditions extremely
unstable and summer thunderstorms are not uncommon. As in June these usually
develop over the mountains in the East of the Emirate where the mountains act
as elevated heat sources and where convergence often occurs. Sea breezes on the
east coast force very humid air up the mountains where it combines late in the
afternoon with Gulf coast sea breezes from the Northwest. Inland stations
frequently report Towering Cumulus and Cumulonimbus with thunderstorms, squalls
and dust or sandstorms. Mid and upper level easterly winds then help to
propagate the storms towards the Gulf coast where they can occasionally affect
Dubai, Sharjah and the northern Emirates. Mean maximum temperatures in July are
typically around 41°C,Inland Stations being the hottest with expected maximums
of 44°C and all time extremes around 49°C. Sea temperatures begin to become
unpleasantly warm reaching 32-33°C.
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August
Conditions during August are similar to those experienced in July in terms of
temperature and humidity. During the summer as the sea surface temperature
rises, the Gulf increasingly becomes a prolific source of water vapour.
Afternoon sea breezes bring this warm, humid air to coastal areas and can
produce some of the years most uncomfortable conditions. The risk of summer
storms persists and although most frequent over the mountains can occasionally
affect coastal areas. Inland desert areas, have a rather different climate,
although summer maximum temperatures in the desert are frequently higher than
those on the coast the mean humidity is up to 20% lower than coastal areas.
This produces rather more comfortable conditions and is the reason that, prior
to the prevalence of air conditioning, many local families would spend the
summer months away from the coast. Mean sea temperatures are around 33°C but
have been recorded as high as 35°C.
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September
As temperatures begin to fall after the height of the summer there is a sting
in the tail for residents of coastal cities. Sea temperatures reach a peak at
the end of August and it is therefore during this time that the potential for
warm, humid air to be advected to the coast reaches a maximum. September is far
from being the most humid month but it has the highest humidity of the hot
summer months. For this reason September is extremely humid and is one of the
months with a high occurrence of fog. Night time temperatures begin to drop
into the upper 20’s °C and fog will often form in the early morning hours.
Maximum temperatures can still occasionally reach extremes of 45°C with extreme
minimum’s around 22°C. Sea temperatures begin to fall later in the month with
the mean for the month of around 32°C.
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October
It is the latter part of the year when the weather is the most pleasant and
settled in the UAE. Maximum temperatures in October are around 35°C and
although the humidity remains reasonably high comfort indices have fallen from
the extreme levels experienced in the summer. As night time temperatures
continue to fall, faster than the sea temperature, fog is still a problem in
the early morning hours. The weather is usually dry and settled but there have
been exceptional years such as 1997 when several weather systems penetrated
into the area bringing unsettled wet weather and thunderstorms. The mean sea
temperature for the month is 30°C.
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November
Temperatures continue to fall sharply during the month with mean maximums
between 30°C and 31°C. As the subtropical jet moves southwards and upper level
winds over the Gulf strengthen there is the increased potential for low
pressure systems to propagate from the North and West into the area. Late in
the month it is possible for the first Shamals to affect the Gulf but it is not
usually until December that unsettled weather reaches the region. Again
November 1997 was an exceptional year with twelve rain days including four
thunderstorm days producing 31 mm of rain at Dubai International Airport. In
2004 a severe line squall and thunderstorm brought heavy rain (24 mm) and a
hail storm that produced stones of up to 1.5 cm in diameter.
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December
By the end of the year winter systems are more frequently affecting the
Emirates, the mean monthly rainfall is 15 mm with rain reported on three or
four days during the month. Mean maximums have fallen to 26°C with minimum’s
typically around 16°C. The humidity is frequently high in the early morning
hours with fog still causing a problem, although Dubai and the Northern
Emirates tend to be a little less humid than other areas of the country.
Occasionally persistent periods of unsettled and wet weather can affect Dubai
in December. Rainfall totals have been as high as 130 mm with a 24 hour maximum
rainfall of 73 mm. Sea temperatures fall to around 23°C.
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