We want to visit Australia and NZ last week of August and first week of September...what is weather like at that time? Fares are cheaper at that time.

Australia is a big country - in August you can be sunbaking in 33 degree heat in one part of the country, and freezing in another area. Queensland will be delightful but southern states will be cold and wet. Tell us which part of Australia you plan to visit and we can give you a sensible answer.

New Zealand will be on the cold side, and weather unpredictable. I like visiting NZ in the winter though, fewer people, cheaper accommodation (outside of ski areas of course). You legally have to carry snow chains in your car in some areas at that time of year - like Milford Sound. Cold is relative though, NZ doesn't get nearly as cold as say, Colorado.

How long are you planning for each country?

https://www.buzzfeed.com/simoncrerar...ustralian-maps

As noted, Australia is a big place & weather patterns vary quite a lot.

Dismal in New Zealand..better in Australia.
However don't let that put you off NZ! It rains here a lot but you'll be visiting in the quiet time so that's a huge advantage. Bring a rain jacket and good shoes/boots if you want to do any bush walking. It never gets as cold as Colorado!
Up in Cairns it will be around 25 degrees and would be the perfect time to visit. We went in May which was fine.

Two weeks to see both Australia and New Zealand?

We have decided to go the middle of September, so weather should work out better. It is the only time of year we can get away. Thanks for your help

Australia's official weather forecasts & weather radar - Bureau of Meteorology for weather forecasts & records in Australia.

"southern states will be cold and wet." An exaggeration I would say. Even in winter you'll have plenty of lovely weather in places like Sydney and Adelaide with clear skies and highs in the 60s and even 70s. I wouldn't discourage an August trip at all (been there many times at that time of year).