Wondering if I could tap into the knowledge of those that have first hand experience...
Thinking about a trip in Spring/early Summer, California to Florida. How bad are the storms and what time of year would be the best? Hoping Spring... maybe?

 

Spring WILL show you some serious Thunderstorms all across the Southern E-W corridor.
I've done coast-to-coast in the Fall....early/middle November, and found it to be the best choice.

 

Starts to get cold in November, doesn't it?

 

I'd rather do that ride in the spring than summer, all things considered. You might have to deal with cold weather along the 40 in Flag or Albuquerque, not out of the question there could be cold or icy conditions in the pass outside of ABQ. Just gotta watch the weather and decide when to drop down to the 10.

In the south, you get a break in the rain in the spring. Cold fronts are going through every couple of weeks through Feb. Afternoon thunderstorms start getting cranked up in June. In the spring it tends to be less humid, it's one of the nicest times of the year. Yeah November is glorious in Fla but March-April ain't bad.

You can really run the 10 any time of year, I got really unlucky one January and ran into a lot of gross weather east of Tucson but in the spring you should be fine.

If it was me I might ride through Joshua tree and take the 10 corridor the rest of the way. I'd consider detouring thru Tombstone and Bisbee. From El Paso I might take 90 through Marfa and Alpine, love that part of Texas. I'd work my way up to the other side of the highway, cut across hill country to Austin, take 290 down to Houston. Try to get through that at night or really really early in the morning. Can't stand Baton Rouge, had a nice trip down 90 through Morgan City once and frankly I'd rather run the gauntlet through New Orleans than battle the 12. Poker stop for sure in Biloxi which is a pretty town, you can often get a great deal on a plush room at one of the casinos. Mobile is also pretty, just try to avoid rush hour. Get off on 98 to see Destin, Fort Walton. Might be spring break in PC, might be slow going through there but scenery should be good. Stop off and watch the F22's doing touch and go's at Tyndall. If Appalachicola still exists, stop off and get some oysters. I'd stay on 98 as far as Cedar Key, spend the night there. Then decide where else in Fla you want to go. You'll have fun, there's some good times along that road. Key is to not just blow through on the interstate and miss all the good stuff.

 

I've done it in mid-may and the weather was mostly great -- San Diego to Jacksonville. A cold front did come in on the way back. We left Houston in beautiful weather and it was pretty cold by the time we got to Dallas. Windy most of the way across Texas to Amarillo. Really can't complain about that though.

 

Not along the Southern route (I-10 and the non-Interstate highway routes that parallel it). Lower elevations and all that...no problem. The only rain I hit of any significance all the way across from the Georgia coast and back was during short side-trip, running from from Carlsbad Caverns down to El Paso. Pulled into some kind of "Mexi-Mart" convenience store outside of El Paso about 1:00 am. After riding through all that rain/road spray, etc., me and the bike were carrying a coat of gray/brown mud all over us. Must have looked like some kind of Ghost coming in out of the mountains...Got a lot of attention from the Vatos hanging around in the parking lot. Enjoyed a cup of coffee sitting outside at a picnic table...then back on the bike, and on into El Paso.
(Please excuse the digression...lottsa great memories that sometimes just spill out )
Farther North...yes. I ran x-country through Nebraska, into Colorado once. Even in the first week of June..temps in the higher elevations ( Vail Pass for example..) were "chilly" for sure. Upper 20's if memory serves...I wouldn't even think of trying that route in November.