Rain ain't gonna hurt a thing unless it was to the extent it literally washed fertilizer away or lime. Which, on surface, I suppose it sure is possible with enough rain but I doubt it's common.
the Nitrogen in your fertilizer, you better have had rain within 24 hours. The N part of the #'s.... 13-13-13, N-P-K in other terms, the 1st 13 is the Nitrogen is the most important by far for brassicas and the one most likely to go by-by from not preparing right. N fertilizer is an encapsulated GAS so it will literally evaporate within 24 hours if not covered (disced in, tilled, whatever) or good amount of rain. Not the case with P-K or lime.
Reminder, whatever the # is... It's a PERCENTAGE of what's actually there per 100 lbs. So, 13-0-0 for example VS 46-0-0.... You literally would have to put about 3 times as many lbs of 13-0-0 to equal what 46-0-0 puts out for N. (46-0-0 is Urea and the most concentrated form of dry N). 13-13-13 for example is simply a fertilizer that's filled with mainly filler that doesn't do anything. Just pay attention to the # and consider it a % of actual. What you ACTUALLY put down is what is important, not the amount of lbs you put down because 2 different bags of fertilizer are not created equal.
Without a soil test, ACTUAL, what I'd want down ACTUAL (remember, 46-0-0 is only 46 lbs of N for each 100 applied) would be around 150-100-100 if you can afford it. P&K at this point are mainly going to be for subsequent years as most won't break down this season but I'd include. N shows the fastest & biggest benefit to plants but over time, missing on P&K, wrong PH's (add lime if called for) & even things like micronutrients (to a smaller scale, especially if you're doing Dbltree rotation) - all this will have huge long term impacts to your plots. Proper fertilizer and step following (Plus weather that cooperates, etc) = excellent plants & plots. Skimping or skipping fertilizers = crummy plots, little brassicas, ill colored brassicas and stunted growth that often all goes to waste. Do it right. Plant it right, follow the steps, put in the proper fertilizers and amounts, you will not regret it.