If you find that you cannot get Freeview working after a storm or any weather event then the likely case is that your antenna that you use to receive Freeview has been damaged or repositioned, there might be more reasons why you cannot view Freeview but below is a list of links and tips to ensure that you are connected back, its best to contact your local installer if you feel something is not quite right. 

Ensure weather conditions are right if you are considering any DIY on correcting aerial faults or outside maintenance. 

I see a NO SIGNAL on my Freeview receiver/recorder

Your satellite dish could have been damaged or readjusted by the wind, Please check that your dish remains in tact, You will need to get a installer (or yourself) to realign your dish to the correct Satellite (Which is Optus D1) and you can find out more on how to do this here

Another cause might be to do with your Satellite Cable which is connected from your dish. This could have been damaged, ensure that the lead is clean from any cuts or obvious bends as this could affect your reception 

I am seeing a picture but its pixelated and sometimes squeaks out pitch tones 

If there is heavy weather conditions outside then the Satellite signal will encounter a "RAIN FADE"  A rain fade occurs when the line of sight to the Satellite in the sky is interrupted usually by heavy rain and/or thunderstorms. You may need to wait untill conditions improve before normal pictures return. If you still have this issue please consult your local installer or realign the dish to (Optus D1) here

I can only watch one group of channels (e.g. TVNZ 1, TVNZ 2, TVNZ 1 +1 , TVNZ 2 +1)

Channels on Freeview Satellite are broadcasted to you using different frequencies, some of these frequencies are weaker or stronger than the rest so it might be best to check your satellite dish and get a installer (or yourself) to realign the LNB (Little machine in front of the dish) or the dish itself.  You can have a look at the different frequency groups here

These help topics are generic and are provided from the community, your Freeview situation may be different and recommend a installer to check out your setup.