It's like going from zero to 60 in five seconds.
May in the foothills was wet and cold. Clouds built in on Mothers Day, the air chilled and snow flew above 3,000 feet - just as the dust from Sonora's Roundup Rodeo was settling.
Spring was half over, but it seemed like winter would never end.
Fire? You'd need napalm to start one.
But here we are, a month and a half later: Burning permits have been canceled, a weekend fire blackened more than 100 acres of grass near Copperopolis, the mercury has skied to 100 degrees and beyond, and huge crops of dry grass and brush below 2,000 feet are highly volatile.
With thus backdrop, Yosemite National Park has ignited its first controlled burn since last August's Big Meadow Fire jumped its lines and ravaged 7,500 acres.
This all comes with the approach if the Fourth of July weekend and its annual influx of visitors and fireworks both legal and illegal.
All of which gives rise to more than a few questions:
• Is it time to get ready for fire season?
The initiated know it was time to clear brush and debris from around your homes six months ago, when the sodden earth made a fire harder to start than a 1951 Buick Roadmaster left in a pasture for two decades.
Now, particularly in the low country, a spark from a lawnmower blade can start a fire in just seconds. So cut and trim your grass and brush at dusk or early in the morning, when temperatures and humidity are low.
State law requires owners to clear dry grass, brush, debris and overhanging limbs from within 100 feet of their homes, creating what firefighters call "defensible space."
The law notwithstanding, many homeowners are living dangerously. "I've never seem so much fuel around homes in all my years in prevention," said Rommie Jones, prevention bureau chief for Cal Fire's Tuolumne-Calaveras Unit.
A tight economy, which both minimizes state enforcement efforts and makes clearing harder for homeowners to afford, may be to blame.
• What about debris burning?
Forget it until October or November. Permits were suspended last week. And here's some good news: Even during the April and May burn season, escaped debris fires were way down - meaning people are being far more careful.
• And fireworks? Legal in Calaveras County, illegal in Tuolumne. Potentially dangerous everywhere.
• How dangerous are today's conditions? Below 2,000 feet, highly. Use extreme caution.
At most locations above 4,000 feet, said Jones, "it's not gonna happen." Heavy winter rains have left timber and soils moist and, for now, reasonably safe.
Stanislaus National Forest spokesman Jerry Snyder agrees, pointing out that some high country campgrounds and roads are still closed because of mud or snow.
Continued hot weather, both Jones and Snyder warn, could change this quickly.
• Is Yosemite really doing a controlled burn?
Yes. Tests went well, conditions are favorable, and the National Park Service ignited a fire aimed at charring 200 acres of underbrush in the Crane Flat area before the July 4 weekend throngs arrive.
For those still edgy because of last year's Big Meadow fiasco, know that Yosemite now has a new superintendent and a new set of controlled-burn rules aimed at preventing a recurrence.
This is the beginning of a long, hot fire season that typically extends into October. Tuolumne and Calaveras counties have dodged catastrophic fires over the past several years, and public vigilance is no doubt part of the formula for success.
So, to paraphrase Sgt. Phil Esterhaus of "Hill Street Blues," let's be careful out there