Easter Weather & History

Easter Saturday should be spectacular, Sunday not so much, but here is the forecast:

Easter IS unusually late this year.  Jim Todd sent this great bit of Easter information to us today.  Jim runs the Planetarium at OMSI.  I’ve always had a keen interest in history…if you do as well, you might want to read on…

This question comes up every year, with a bit of puzzlement, too. But for this year in particular, many people have commented on Easter’s. Do you know why the holiday’s date changes each year? Other major holidays throughout the year have set days: July 4th; Labor Day; Christmas, etc.  It’s often hard to comprehend Easter’s association with the Vernal Equinox, the full moon, and Sunday.

Each year, Easter’s date bounces around the calendar.  Why is this?  In 325 A.D., The Council of Nicaea, commonly regarded as the first Ecumenical council of the Christian Church, convened in ancient Nicaea (now Iznik,Turkey) at the request of Constantine I. His goal for the council was to restore order in the young religion of Christianity, then beset with internal disagreements and controversy.  

As a side note, the council was also instructed to arrive at a means for calculating the annual observance of Easter, which at the time coincided with the Jewish holiday of Passover. Throughout Constantine I’s kingdom, the Christian Passover or Easter was observed on different dates. Attributed to Pope Saint Soter and followed by believers in Alexandria and Romewas the formula which is followed today: Easter is observed on the first Sunday after the first full moon following the vernal equinox. This neatly avoided following any particular calendar, and staggered both Jewish and Christian holidays.

 How did the moon get involved in all this?  The number of lunar cycles in a year is uneven.  This means that the time of the Passover celebration is a moveable feast during the month of March and April.  The council of Nicaea involved the full moon to provide the pilgrims, who traveled to Jerusalem, with a bright night sky in order to assure their safety.

 For Easter in 2011, the vernal equinox is on March 20, the time when the sun is directly over the equator.  The full moon for March is on the 19th, before the equinox.  In April, the full moon is on Sunday the 17th.  But church astronomers added further stipulation that if the first full moon occurred on a Sunday, then Easter should be celebrated the following Sunday.  In this case, Easter 2011 will be on Sunday, April 24.  This is just a day short of latest date possible of April 25.  The last time this occurred was in 1943 and the next time it falls on April 25 is the year 2038.  The earliest date is on March 22 which happened in 1818 and will not happen again until 2285.

60 Responses to Easter Weather & History

  1. bgb41 says:

    Certainly not going to get my 8th freeze of April tonight out here at BG Lake. Last hour or so the east winds have broke through here and temperature is stuck at 50 deg with 31% humidity and a breeze. I think East Battle Ground may stay in the 40’s all night tonight while areas further west and south will be 30-35 in Brush Prairie / Dwntn BG.

  2. Peaked at 62 here in BG with an east wind to just 17 mph. Dewpoint bottomed out at 20. Not often you see that in April!

  3. Timmy_Supercell (Klamath Falls @ 4200') says:

    Nice day, 53F and finally light winds! It’s always gusty/blustery in my area (especially on clear days) but this time I could bare standing outside without a big jacket on.

    Anyhow it’s almost May and time sure did fly since I moved here.

  4. What a nice day!
    High 59.4F
    Low 29.7F

  5. Is it really 71 in the Dalles or is the thermometer in the sun? It’s not unheard of to be warm (and burning hot in the summer!), but it seems a bit out of place. The webcam says it’s that warm there.

  6. Tyler in Battle Ground says:

    I’ve picked up an east wind and my temp is up to 62 but my dewpoint dropped from 36 to 22.

  7. W7ENK says:



  8. bgb41 says:

    Downsloping is obviously occurring now in Clark County. I am sitting at 63 now after a low of 29 this morning. I have 27% humidity and also noticed a renegade cumulus cloud at about 850mb level drifting slow from est to west. Spectacular afternoon here.

  9. Rob "Wrath" S.E. Portland says:

    What an incredibly nice day today! I just got back from a very busy Crown Point with the Family and it was becoming breezy there, but the bright sun shine and visibility was great.

  10. Kyle From Silverton says:

    Here is the latest temps: Aurora | 53 °F | Clear
    Salem | 49 °F | Scattered Clouds
    McMinnville | 57 °F | Clear
    Portland Troutdale | 58 °F | Clear

  11. Kyle From Silverton says:

    Except the two historic artic outbreaks happened in November and very late February so in truth we only had ONE historic outbreak but we just cannot have a cold January anymore without inversions.

  12. bgb41 says:

    This morning marked 7 nights below freezing in April 2011 at Battle Ground Lake:

    Here are the dates so far at 32 or lower for a minimum

    1)—04-07 – 32
    2)—04-08 – 27
    3)—04-12 – 29
    4)—04-17 – 28
    5)—04-18 – 28
    6)—04-19 – 30
    7)—04-22 – 29

    • W7ENK says:

      Just out of curiosity, what would qualify as a “hard freeze”?

      March 2, 2011 – “Winter Is Over”


      Second graphic…

      Unlike some people, I’m not trying to hold anything you said over your head, Mark… I’m just pointing out that despite everyone’s best predictions and wishes, this winter seems to have held on quite a bit longer than anyone had expected!


    • Mark Nelsen says:

      A hard freeze would be lows maybe 20-25 degrees at PDX. Since that March 2nd blog post (I also said the same thing on-air), PDX has been all the way down to…31. And even the coldest outlying areas haven’t been below 25.

      Notice in that posting I said “there will still be frosty nights when you need to bring in plants”. Frost should be expected at times in any early Spring in Western Oregon.

      I’d say the 2nd graphic was perfect. We still had some snow in the hills a couple times after that, and no flooding, freezing rain, or metro area snowfall.

    • Jesse-Orchards says:

      I know most farmers consider a “hard freeze” 28 degrees or lower, in which case I and many other metro locations have seen several since early March.

      • Mark Nelsen says:

        Maybe I should have used the term “arctic blast”. The point was that after early March we weren’t going to get a pipe-freezing cold spell.

    • Aloha Rainshadow says:

      Good thing most of us are not farmers!!!

  13. Kyle From Silverton says:

    I call this winter the 10 day model winter where nothing exciting could get out of day 10 on the models.

    • Jesse-Orchards says:

      We had two historic arctic outbreaks in the winter that managed to get out of the ten day range.

      Also meteorological winter’s been over for almost two months.

  14. Andrew Johnson says:

    I hit 28 earlier this morning. I believe its my 6th sub-freezing low of the month.

  15. Mike (Orchards 255') says:

    Down to a cold 31.2° this am..

  16. Cherie in Vernonia says:

    brrrrr….still 35 here. Come on sunshine!

  17. GFS continues to weaken the system for Sunday, now showing just a little rain and not even completely cloudy.


  18. hiophil says:

    With a low of at least 30 at KHIO this morning, that makes it the eight day this month with an overnight 32 degree reading or lower.

  19. GFS continues to show warm weather around the first of May. Perhaps the low to mid 70s.


    The Euro agrees:


    Let’s hope that holds!

  20. 30.1 for a low here but the sun is out and we are quickly warming!

  21. Roman~Snow-Zone says:

    WOW. 28.9F for a low here at my house in Monmouth.

  22. bgb41 says:

    00Z GFS – http://i54.tinypic.com/2afd4yv.jpg

    There are 7 days over 60 on this latest run.

    • Ryan (Walnut Grove) says:

      I just need that dry and warmer air to fast forward about 24 hours! I have a girlfriend to propose to and I need a dry morning April 30th for my plans to go through.

      Them models have been going from dry and mild to decreasing showers and cool.

    • Cherie in Vernonia says:

      congrats Ryan!

    • Ryan (Walnut Grove) says:

      Thanks. I’m looking forward too it. 🙂

  23. bgb41 says:

    4/22/2011 Oregon (All) Temperature Summary

    High:58 at AGNESS2( 247 ft) & CW5302 Roseburg(410 ft) & DW5789 Eagle Poi(1463 ft) & MEDFORD PORT #2(1858 ft) & UMATILLA(270 ft) & Echo(680 ft)
    Low: 44 at Clatsop Spit(30 ft) & Fremont Bridge W(270 ft)

    High:20 at Mount Hood Meado(6601 ft)
    Low: 12 at Mount Hood Meado (6601 ft )

    Largest Diurnal Change: 26 degrees
    BEND WATERSHED (45/19 ) (5330 ft )
    CABIN LAKE (45/19) (4560 ft)

    Heaviest Rainfall:
    0.60″ at DW3387 Lakeview(5358ft)
    0.59″ at BASQUE HILLS(5080ft)

  24. Karl Bonner says:


    The last frame of Mark’s EURO is looking warm now. That would be for Sunday May 1.

    One thing I am curious about is whether the warmest temps this Saturday will be centered in the Willamette Valley or in the East Gorge/Lower Basin…We’re getting to the time of year when the interior tends to have the thermal advantage, but sometimes we get a curve ball nonetheless…

  25. Boydo3 N. Albany 500' says:

    Nice summary of how astronomy and astrology is woven into our Judeo-Christian culture. I wonder though, how much of the the Anglo-pagan rite had to be incorporated into the structure to draw the rest of us heathens into the fold. Our pale ancestors spent a bunch of time gazing at the moon and stars. They no doubt forced a lot of negotiation with the carriers of the New Idea.
    Given how funky the climate was back then, Spring time could only bring hope to the people who had survived the long winters.

    • Karl Bonner says:

      Many Neopagans incorporate the egg and hare as symbols of the vernal equinox, usually called Ostara. In fact, the name “Easter” is more closely related to Ostara than anything Judaic. (This year Easter is only seven days before May Day, which is another important holiday in both Paleopagan and Neopagan calendars.)

      Of course, the fertility symbols of the hare and egg aren’t too phenologically relevant to the vernal equinox in the northern half of Europe, where the landscape in mid to late March is still very dark and lifeless. In Celtic and Germanic tradition these themes are associated mainly with the month of May. But in the Mediterranean, late March is a very flowery and lively time due to the warmer climate. Here in the Pacific Northwest, low-elevation places south of the Puget Sound and away from the immediate coast are probably somewhat ahead of the British Isles and North Sea region, but quite a bit behind the Mediterranean.

      Actually, this spring in the Northwest is probably a good representation, both in terms of temperature and phenology, of a “normal” spring in NW Europe, where wintry chill and plant dormancy linger a bit longer into March and April than they usually do here. I’m not sure if Oregon’s ever gotten a year where our spring is as early and warm as the Mediterranean, but the first part of spring 2005 and 2010 probably come the closest, at least for late February and March.

  26. Paul D says:

    You have me to thank for the warm dry weather. I finally get someone to put down new sod in my yard, and what happens? It quits raining. I knew it would happen….. When I want it to rain, it won’t. Now I’m going to have to run my water sprinklers in April. Sheesh….

  27. Walt Hellman says:

    The moon is most likely involved because the whole Jewish calendar is lunar. As I understand it they wanted to distinguish Easter from Passover because Christianity was separating from Judaism, so to keep away from Passover they probably had to stick with the same lunar calendar. You have to be on the same type of calendar to avoid the holidays happening on the same date.

  28. W7ENK says:

    While on my walk with the dog this evening…

    It’s nice to finally see our beautiful sunsets becoming more frequent, especially after such a long time under the clouds and rain, but I wish it would warm up now…

    Interesting that it’s almost May, and yet 90% of the trees in my area have yet to leaf out… it’s been a strange, cool, slow start to spring, that’s for sure!

    • Karl Bonner says:

      Have you taken any photos of the repressed spring plant activity? I’m just about to post mine.

    • W7ENK says:

      @Karl – In the one photo posted here (above), the trees look like it’s the dead middle of January…

      Other than that, no, I haven’t taken any photos.

      I did notice that the only trees that seem to be leafing out around the Milwaukie area are the big cottonwoods. I started smelling them last weekend, now they’re starting to turn green, I’d say maybe only 35 or 40% full “bloom”, but still noticeably repressed, though certainly farther along than anything else. Walnut, maple (multiple varieties), sweet gum, alder – everything else is still bare. There is one Chestnut at the bottom of my street that is also starting to leaf, but it’s way behind the cottonwoods just around the corner, I’d say maybe only 25% MAX.

      The only deciduous thing in my yard currently bearing leaves is my avocado, but it’s an evergreen.

  29. Nice history article. I was going to look it up eventually but you saved me the work 😉

  30. One tiny shower and it’s just pouring here right now! Wind is blowing 20 mph lol.

  31. Mike near Clackamas Town Center says:

    Wow..Sunday will be a special day not only because it’s easter but because it will land on my 30th birthday 🙂 Hopefully the weather will be as nice as Saturday but not holding my breath.

  32. bgb41 says:

    Here is a new climate data page I constructed today. It compares each month from 1961-2010 at PDX to the new calculated 1981-2010 30 year averages. Blue shaded temps are below and red are above for cell values. Precip values in green are above normal and red are below. I am adding much more to this page the next couple of days.


    • bgb41 says:

      I suggest right clicking on this link and opening in a new window so the frames aren’t scrunched together in this narrow wordpress window.

  33. Garron near Wash. Square says:

    Thanks for the refresher Mark. As complicated as that answer is, and all the added implications over time, you’d think there must be a calculus formula that sums it up easier than that…lol Thanks again and Happy (later than usual)Easter everyone!!!!!

  34. Sandi (Wilsonville) says:

    Technically, the council was forced by Constantine to move the resurrection day, known as First Fruits in scripture, away from passover and the times specified in Scripture to an existing Roman holiday known as Ishtar. It kept the calendar simpler for them, as stated above and added extra traditions not previously associated with First Fruits.

    I hope we can welcome in some warm weather now!!

  35. Mike (Orchards 255') says:

    Great write-up Mark!….Anything over 60 would be just be fine with me.

  36. Interesting! Well I hope we hit 70, I want it badly!

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