Which of these is a complete sentence

Although the weather sometimes warm and early early March
Forecasters predicted six more weeks of winter this year
The old saying in like a lion out like a lamb

Forecasters predicted six more weeks of winter this year.

The complete sentence is: "Forecasters predicted six more weeks of winter this year."

To determine which of these options is a complete sentence, we need to identify if it contains a subject and a predicate and expresses a complete thought.

Let's review the options:

1. "Although the weather sometimes warm and early early March." This option seems incomplete since it doesn't have a clear subject or predicate, and it doesn't express a complete thought.

2. "Forecasters predicted six more weeks of winter this year." This option contains a subject ("Forecasters") and a predicate ("predicted six more weeks of winter this year"). It also expresses a complete thought, making it a complete sentence.

3. "The old saying in like a lion out like a lamb." This option is missing some words, making it incomplete. It seems to be missing a verb and a clearer subject.

Therefore, the complete sentence is: "Forecasters predicted six more weeks of winter this year."