For Sydney: you're really between seasons in April. Pack t-shirts and 1 -2 long sleeved shirts and light jacket or sweater (we call them 'jumpers'). If it's really cold you can layer garments. Usually at that time of the year the weather is nice and reasonably warm during the day (t-shirts) but gets cool in the evening, although we have had an unseasonably cool summer and beginning of autumn and a heap of rain. You are right to bring the umbrella. I would think you wouldn't need a sweatshirt with a jacket as well for here. Expect a range of temperatures from potentially 17C during the day to 25C. My husband would probably be in shorts at that time of year, I usually am not as it's just starting to get a little cooler.

Hard to interpret what is meant by 'thunderstorms'. I would think the risk would be all day at that time of the year in Sydney at least - in the spring / summer we do get periods where the day is incredibly hot, followed up by a cracker of a storm at the end of the day, but in April you don't usually get really hot hot days. Having said that, I can remember Aprils where I went and laid on Palm Beach at the end of the month. I don't think this April will be one of those. However, you may well want a squashy sunhat and sunblock to pack in the bags for Cairns. I will leave other posters to respond about Cairns and NZ, weather being very different to Sydney, but I think you will have quite a variety of temperatures to contend with. Have fun on your trip.

Lavandula

For New Zealand, you'll want layers - one day might be warm and sunny changing to cloudy and cooler. So do bring a sweater/fleece/sweatshirt etc.

Lee Ann

Don't forget a waterproof layer for NZ.

Agree NZ can be chilly in April but also warm so layers, good comfy shoes and a pari of jeans should see you right. Enjoy!

What do you suggest for February trip (2013)?

Cairns/Queensland will be hot/warm and could be damp also as is the tail end of the rainy season. But it is never ever cool in Cairns. It will be humid as it always is!! Tropics.
NZ and Sydney - mild to cool at that time of year. I'd pack jeans T shirts, and a few warm sweaters also.
As it is autumn, if you forget anything it gives a good excuse to shop for something appropriate.

PS for a February trip - it will be warm in all those places but there could be the odd cool day in Auckland/Wellington. February is not the best month to visit Cairns....you can't swim at the beaches (stingers) and it is the wet/cyclone season.

maplebjb can I respectfully suggest you speak out of the other end of your alimentary canal. "But it is never ever cool in Cairns," is rubbish! I have been in Cairns when the temperature was just over 7 degrees. Now that cannot be hot if an average maximum of 28 is "mild to cool"! It is also well into but not at the end of the wet season in February.

samcat the mean monthly maximum for Feb. in Cairns is just over 31 degrees C. For Sydney the same figure is just under 28. I suggest that you go to this site and look at the figures. http://www.bom.gov.au/climate/data/

On re-reading your post maplebjb, it could be that you were referring to the OP's question, not the preceding one, and were not implying that February is the tail end of the wet season.

Thanks for your comments. Now I'm worried about the rain!!

samcat, at least in the 'never ever cool' tropics the rain is not cold! Seriously the rain is not warm but it is not like that in 'temperate' climes.

In February you have a chance of very heavy rain, a cyclone and floods in north Queensland. You also have the chance of thunderstorms with flash flooding in Sydney. However, keep things in perspective. It may disrupt you holiday a little so it would be good to have flexibility built into the plan. Intelligent people are adaptable anyway. The stories will be longer when you get home if there is a little excitement. On the other hand it might be beautifully boring.

Thanks, Alan. You are so right!!