I answered a related question, and I'm copying most of the answer here...

Film manufacturers classify films as "professional" or "consumer" films...or at least they used to, back when film was in high enough demand to warrant producing many more varieties. Professional films were designed to be stored cool until the day of exposure, and it was very common to see refrigerators in camera shops storing film for sale - I still see some. Consumer films were designed to reach their optimal colour balance without refrigerator storage - manufacturers were well aware that these films would sit on camera store shelves, and indeed sit in consumers' cameras for up to a year maybe before processing. As long as you kept the film expiration date in mind, and didn't store your camera in a car's glove compartment, things were generally fine.

For example... Fujifilm Velvia, Astia and Provia are/were professional reversal films, and Fujifilm Sensia was the consumer "equivalent". Kodak had the Ektachrome family of professional reversal films, while the consumer equivalents were branded "Elite Chrome".

In practice though...none of this is really critical. A few weeks or months in sub-par storage conditions is not going to have a significant effect on in-date film. Just buy fresh film (i.e. from a reputable vendor with reasonable stock turnover, selling non-expired film), don't store it somewhere that is subject to high temperatures, direct sunlight or high humidity/moisture, use the film before the expiration date printed on the box, and have it processed without too much delay.

Here is some information from the Kodak publication KODAK Color Films: The Differences Between Professional Films and Films for General Picture-Taking:

All color films are manufactured in a similar manner. They are composed of several layers of complex emulsions made of different chemical compounds. Because these compounds tend to change slowly with time, all color films will age, beginning on the day that they are manufactured. As films age, their color balance and other characteristics may change slightly.

To provide films that meet the needs of different kinds of photographers, Kodak allows for this aging process during manufacture. Kodak builds a small manufacturing bias into films for general picture-taking to compensate for changes produced by typical storage conditions and delays between purchase and processing.

Regardless of the film type, you should use all films before the expiration date printed on the carton. You will also obtain the best quality when you process the film promptly after exposure.

Kodak professional films are close to optimum color balance when they are manufactured and packaged. The film will remain near this balance if it's stored as recommended in the instructions or on the film carton and processed before the expiration date on the carton.

Casual picture-takers usually buy one or two rolls of film at a time. One roll of film may remain in the camera at room temperature for several weeks or even months before processing.

Under normal temperature conditions of 24°C (75°F) or lower, Kodak color films for general picture-taking do not require refrigeration. Storing them at room temperature allows the film to mature to its aim color balance and speed.

One point worth mentioning again, as bvy points out in a previous answer, 135 film is designed so that the film inside the canister is protected from light. You can leave the canister sitting around without fear that light will expose the film inside.