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PapaJohnTravolta t1_jdfbv2y wrote

Reply to comment by ceededcrotch in massive fire on belle isle rocks by ceededcrotch

We’re in the seasonal burn ban from February to the end of April, you’re not allowed open air burns before 4:00pm. It’s always dry this time of year.

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lunar_unit t1_jdfczko wrote

I've always thought it was a strange rule. Why after 4pm? Do fires not make bigger fires after 4pm?

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wagonboss t1_jdfe7kj wrote

Humidity.

humidity drops from morning through early afternoon, and the drier the air- the easier it’s spread. After 4, as the evening settles, humidity raises and doesn’t burn as easily

Source: Firefighter

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wagonboss t1_jdh83mg wrote

Thanks to all for the upvotes, just a little more of an explanation for ya. It’s not a perfect science, and I’m not a meteorologist- so I’ll do my best. In the morning humidity is typically higher from overnight. As temperatures rise, humidity drops. When it’s below 20% and combined with dry conditions and wind, it becomes very conducive to fire spread. So the 4pm burn law was created to skip the worst of it. Usually it starts to raise before that time, but it’s a compromise as I’m sure when the law was created there was some push back. Today the humidity doesn’t dip super low, but here’s an example of it raising throughout the afternoon:

https://preview.redd.it/gl4vrvwdtppa1.jpeg?width=1202&format=pjpg&auto=webp&v=enabled&s=7a0e206e4f15b0937e2a66d243be1043a28fa7c9

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KiwiStack t1_jdgyysw wrote

Oh… this makes a lot more sense. Growing up in an area with volunteer firefighters, I always thought it was because they had more firefighters on shift after four.

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geneb0322 t1_jdfejgu wrote

Humidity levels tend to rise and winds tend to calm after 4:00 making it less of a risk (though still a risk).

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theeandthine t1_jdfelim wrote

Kinda...Like generally it's supposed to be less windy in the evening? So less risk of spreading I think?

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