Flight is delayed 5 days for storms. At that time my schengen visa is expiring. Is that a big deal?

Why would you stupidly travel with it that close to expiration?!

"Unfortunately, unlike other countries like the USA or Taiwan, the Schengen area’s visa validity cannot be extended according to your allowed duration of stay. This means you will have to leave the Schengen area on the day your visa’s validity expires. For example, your visa is valid until June 30, 2017 and your duration of stay is 20 days. If you enter the Schengen area on June 17, you cannot stay any further than June 30 even if you are given 20 days on your visa. The 20 days must be consumed within the validity period of your visa. To avoid any fines or immigration interrogation, you must leave the Schengen area on or before the validity period.

The next thing to do is to go to your country’s consulate office located in the Schengen area. If you are Indian, look for the embassy of India or the Consulate’s office and ask for assistance. Once you have found your offshore embassy’s office, tell them your honest reason why you extended your stay. If your reason is medical or flight cancellation, then you will probably be given an amnesty and the embassy’s liaison will be able to tell you what you’ll need to do. If your reason is work or business, then you will have to prepare to pay a fine of about €500 or so.

The next step to take after seeking help from your embassy is to go to the local Schengen embassy (depending on where you are) and ask for an extension. For example if your visa expired in Netherlands, then you will need to go to the local Netherlands embassy and show your consulate’s letter and let them know why you overstayed. Sometimes the consulates are kind enough to give an extension especially for reasons beyond your control, otherwise you will be fined, you visa will be stamped to indicate that you have overstayed, and your name will be placed in an immigration hotlist.
The first possible consequence that can be given to any tourist who overstays is to be charged a monetary fine. The amount of fine will again depend on where you are exiting from and the number of days you have overstayed. If you overstayed for a day or two, pray that you get a kinder immigration officer who will let you off the hook for free.

The next possible consequence is to be placed in the immigration hotlist. Since you have overstayed, then the immigration officers will definitely doubt your reasons for overstaying; hence will put you in the travellers’ hotlist. You may have difficulty renewing your Schengen visa if your name will be put on that list.

The next possible consequence is to be banned from re-entering the Schengen area. If you overstayed for a month or so, the immigration officers can decide on banning you from re-entering the Schengen area for up to 3 years.

The worst possible consequence is to be deported back to your country. Deportation only happens to travellers who have worked illegally or have done illegal transactions within the Schengen area. If you intend to work illegally and have been caught, expect to be deported right away with a ban of entry stamp on your passport."