Rules, Weather and what to bring?

Rules

Today the new Changi Airport Rule is formally in place. Carry-ons should not contain liquids, aerosols & gels in containers more than 100ml and the total of such content shouldn't exceed 1 Litre.

Weather

Looking good. 90% of the areas are sunny and in the region of 22-32deg oC. But still must bring Torch and raincoat/brolly if wish to visit caves.

When To Go to Taiwan?

Spring can be clear and dry, or wet and grey, or even blighted by a sandstorm from China. Sometimes you get all three conditions in one day.
Summer (June to August) is a great time to visit the east coast, especially for outdoor activities, but be aware of typhoons, which can hit the island from June to October. Summer is not a good time for travel to the outer islands as they are crowded with tourists, and flights and hotels are difficult to secure. Try October to November when rates have dropped but the weather is still great. The cities are always hot and sticky in summer.
Autumn (September to November) is best, as conditions tend to be warm and dry, air pollution is at a minimum, and prices lower.
Avoid travelling during the Chinese New Year holiday as the entire country pretty much shuts down. Some good holidays not to avoid, however, include Lantern Festival, Dragon Boat Festival, and the Matsu Pilgrimage.
In general, July and August, Chinese New Year, and Saturday nights are considered high season and accommodation prices are often double the off-season rates. Outside touristy areas, however, there is little change in price from month to month (only perhaps weekday and weekend).

Weather

Taiwan is sub-tropical:
> the mountains can be chilly in summer (June to August)
> snowy in winter (December to February)

The dry season lasts from November to January in the north but extends to April in the south.
Summer is hot and sticky all over the low parts of the island, with drenching rains in the mountains.
Daytime temperatures in Taipei are around 33°C in summer and 19°C in winter, while the southern regions experience warmer winters with daytime highs of around 24°C (75°F).
In winter monsoon winds can sweep across the island from Central Asia and cool the air by 10°C or more in a few hours.

the above section is extracted from: http://www.lonelyplanet.com/worldguide/taiwan/when-to-go