Onions in room temperature can go bad quickly in hot climate. They can keep up to a month in Winter before mold grows. It is advised not to keep onions in the refrigerator as their odor will spread to other foods. So the other option for keeping onions longer is to freeze them.
Cutting the onion before freezing is necessary, so it is easier for future use as no thawing is needed. However, take note of the following though: a cut onion will have less flavor, but like said, it will cook much quicker. An onion cut too long in advance lose its juice making the flavor even less. On the other hand, an onion will be as hard as a rock if you freeze it as whole. Then you must wait for thawing before cooking. Instructions for freezing onions >>
Instructions
1. Tear off the fibrous part of the onion base and the papery skin, this will make separation of the interior layers easier. Remove ends.
2. Rinse each onion under running water for 1 minute to stop the enzyme effect and dissolve the molecules that cause teary eyes.
3. Chop, slice, cut, or mince the onion. There is no need to blanch this root vegetable.
4. Wrap onion pieces in layers of food wrap and then put in a freezer container or freezer bag. Remember to label and date the container or bag.