Vigan is situated in a Quarterly Age sedimentary plain
called the Vigan - Bantay Plain which is part of the Ilocos coastal
plain. The Vigan-Bantay is bounded on the east by a moderately rugged
Miocene sediments consisting of interbedded sandstones and shale
to very rugged Meta-volcanics and Meta sediment topography; on the
south is the Municipality of Santa where the north -south trending
fault terminates; to the west is China sea; while the northern boundary
opens to the northern extension of the Ilocos coastal plain.
The central part of the plain is characterized by a
dissected ridge of Plio-Pleistocene Age that trends in a northeast-southwest
direction. The ridge divides the Vigan-Bantay Plain into northern
and southern plains.
The northern part of the plain is drained by minor rivers
namely: Bantaoay, Sto. Tomas, and Nauman rivers, while the Abra
River is the main drainage network of the southern portion of the
plain. Abra River meanders within the hinterland but exhibits a
braided pattern across the plain.
The drainage network of the eastern margin of Vigan-Bantay plain
consist of deeply cut valleys whose pattern is strongly controlled
by main faulting trends, particularly those in the northerly and
Vigan is being drained by the Vigan River and Bantay
River, respectively, on the north and on the south by Mestizo River
whose water discharge comes from Bantaoay head water.
The relief of Vigan Bantay plain is actively level to
undulating with a slope ranging from 0% to 8%. Vigan in particular
is generally level with several hills in Barangays Tamag, Bulala,
and Salindeg, sometimes reaching about 50 meters in elevation and
has a slope ranging from 3% to 8%.
The eastern margin of the plain characterized by a steep to very
steep slope, about 40% to 60%, the relief often reaches an elevation
of more that 600 meters especially the northerly and easterly portion.
The dominant topographic feature in the eastern margin
of the town is the Vigan Gap Hill where the continuously shifting
Vigan River cut its way. The Gap Hill is located approximately 10
kilometers east of Vigan.
The City of Vigan falls under the first climate type in the Philippines
which is characterized by two pronounced seasons: the dry season
which starts from the month of November and ends in April and the
wet season which spans the months of May to October. The average
annual rainfall is 190. 683 mm. and the heaviest registered rainfall
is 693. 3 mm.
The average temperature is 26oC. The average warmest
temperature is 30.9oC and the average coldest temperature is 21.1oC.
An average of 7-10 typhoons visits Vigan annually. The average relative
humidity is 81%.
Vigan Weather Condition - Vigan, Philippines Weather Report