there should be commas around "however" in the following sentence " Dewayne had planned to take the last flight out to chicargo It was cancelled, however, because of bad weather.”

Yes, there should be commas around "however."

I assume you know that you should have a period after Chicago.

In the sentence you provided, the word "however" is acting as a parenthetical element to indicate a contrast. The use of commas around "however" would help set it off from the rest of the sentence. However, in this case, there should not be commas around "however."

The general rule regarding the use of commas with "however" is that commas are typically used when "however" is used as an introductory word or as an interrupter within a sentence. In those cases, commas should be placed both before and after "however." For example:
- "However, Dewayne had planned to take the last flight out to Chicago."
- "Dewayne had planned to take the last flight out to Chicago. However, it was cancelled because of bad weather."

In the original sentence you provided, "however" is not being used as an introductory word or as an interrupter. It is simply connecting two independent clauses. Therefore, omitting the commas around "however" is the correct usage in this case:
- "Dewayne had planned to take the last flight out to Chicago. It was cancelled, however, because of bad weather."

Remember, grammar rules can sometimes be flexible and dependent on the writer's style and the context of the sentence. So, it is always important to consider the specific usage and the effect you want to create when deciding whether to include commas around "however."