I don't run in warm weather so this only applies to cool (not cold) temperatures (I guess between 0 and 15 Celsius, 32 to 60 Fahrenheit):

Any run over an hour, I bring water. Over 1h15m, I usually take some sort of food, too. It so happens that on runs over an hour I also walk every 15 or 20 minutes for one minute. I don't stop entirely, I just walk. I use my walking breaks to drink. If I am eating as well, I might try to struggle whatever I am eating (a small square of Ritter's chocolate, for example) out of my pocket/fuel belt in the 15 seconds before I stop to walk so I can start eating right away and also have time to drink in the next minute or 75 seconds.

I find that walking for one minute or so allows me to conserve an even pace throughout my run (or race), or even to achieve a negative split (shorter second half than first half). I just feel energized when I start running again. (I also use the walking breaks for positive self-talk. ) If I don't stop to walk now and then, my speed just gets slower and slower.

BUT: if I walk for more than 90 seconds it will a lot harder to get going.

You will have to experiment a bit to find what works for you...