The Best Time to Go to ...

It's not a comprehensive list but we've been to Argentina in November (for their springtime) and Thailand/Vietnam in January/February (for their spring/summer.)

There are plenty of websites that cover where to go on holiday recommendations in each month, but none will cover airfare and accommodation prices, as flight prices vary significantly depending on the day of travel (weekend or weekday), departure airport/state/country and whether there is a school holiday one week in the month, where prices may be almost double. Accommodation prices for the same night at the same hotel vary depending on which website is used to book it!

Audley Travel based in the UK have a great website that shows the best weather month by month for much of the globe and a "do not travel in this month" category which would give you a good starting point.

1) South America in May (it's Fall there, and quite comfortable)
2) Iceland in the heat of summer (June-August) - long days and cooler temps. Also true of Scandinavia.

Australia is in the Southern Hemisphere so their seasons are the reverse of ours.

No necessarily bad time to travel but good /bad is activity dependent. February is generally a good month for northern hemisphere snow activities but a challenging month for a northern bike or walking tour.

I enjoy Europe during the second half of winter - better snow longer daylight hours and fewer tourists. I also enjoy the shoulder seasons of May and September-October for walking and bike tours - better (warmer but not hot) wreather, longer daylight and before/after peak tourist season.

But the best time to travel is when you can. You may just have to adjust activities. And Hawaii is nice any time of the year.

Canadian Eastern Maritimes--July to Sept.
Northern Europe--June to October
Western Europe--April-May and Sept.-Oct. are best.
New Zealand and Australia--January to March
Mexico, Caribbean and Hawaii--anytime

As an Aussie I would think August to October is far nicer here than Jan - march but I guess it is more about what activities you want to do in each place than the location. For example if you want to swim with dolphins in New Zealand you want warm weather but if you like to ski you want winter. I usually spend heaps of time jumping from this site to lonely planet... I like the tastes and opinions on this site but lonely planet is far closer to my actual budget! I guess the benefit of leave at different times is you can hit specials or particular types of holidays at different times of year. Sorry I could be much help though

If you can ever get away over Easter you should consider Guatemala... cheap, beautiful culture, Chichicastenango (market) Lake Atitilan (surrounded by mountains and little Mayan villages ) Tikal (Mayan ruins) Antigua... beautiful city with volcanoes nearby... Semana Santa... the Holy Week celebrations are just amazing.... especially in Antigua.

Southeast Asia is best in December-February, when it's a teensy bit cooler, but pretty much rainless.

I was in New Zealand in January, then Australia January-February. New Zealand was pleasant (it's a cooler climate by a lot). I was in Melbourne when they hit the hottest day on record (which has since been topped). I would choose spring or fall for Australia, not summer!

I was in Beijing once, in early January. Temps hovered just below freezing but the skies were clear blue and the air was great. Low season, so low prices, and few crowds. I think December would be about the same.

October is a great time to head to New Mexico, Colorado Plateau, Rockies (U.S. or Canadian). December in Death Valley was excellent for me.

Greetings from India.
Well the best time to visit here is from October to March or even April but January can be extremely cold weather though there is no snow here except the hill stations but the fog may become quite dense sometimes even for some days or a week. From may to September is the summer season followed by rains so one should avoid touring here in those days but still in those days also there r great options available in north Himalayan region including Kashmir n himachal Pradesh n uttarakhand. Hope this gives some insight.
Vikas.

What about Africa such as Eastern Africa and also South Africa? Any comments for these locales?

June:
*Avoid the short, heavy showers and you will find that this is a very pleasant month to be in Cambodia with one great benefit being the thinner crowds at the Angkor Temples (Siem Reap).

October:
In the far north of Vietnam (Hanoi, Halong Bay, Sapa, Ha Giang Ninh Binh, Mai Chau & Cuc Phuong) the weather in mountains of Sapa and Ha Giang is dry and clear promising some of the best trekking conditions of the year.

December:
*From December to February you can expect good weather in Thailand’s east coast (Koh Samui, Koh Phan Ngan, Koh Tao, Hua Hin, Pranburi, Cha Am, Koh Chang), with little if any rain, and refreshing winds helping to keep temperatures more moderate.

Hope this gives you more option on where to go and what to do.