Answer
You can go by the data models as stated above, but i tend to treat each year individually. for example all my bulbs came out in early february this year, which they almost always do so in mid to late march. ugh... but oh well. as for lincoln ne, i would wait until next friday to get a look at the 10 day forecast. it looks like you guys are goanna have a little bit of above average temps this year like us here in so cal. going by the 10 day, as well as the averages is a good rule of thumb, as far as planning anything like this. you can do it now, as you wont get down to 32 in the next week or so. but i would wait one more week.