Mills Norrie State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mills Norrie State Park clear sky chart from 2005-11-06 to 2024-11-04.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	16% 7% 3 7% 5% 4 5% 4 6% 7% 37%	101344
	Night	17% 8% 3 7% 4 4 4 3 5% 7% 38%	97662
Transparency	Day	43% 7% 12% 22% 14% 2	104863
	Night	43% 7% 12% 22% 14% 2	102232
Seeing	Day	20% 13% 28% 24% 11% 4	14902
	Night	20% 10% 30% 29% 9% 1	23982

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	14% 8% 3 6% 5% 4 4 4 6% 6% 40%	2517
	11th to 20th	Day	15% 9% 4 9% 6% 5% 5% 4 6% 6% 31%	2520
	21st to end	Day	20% 12% 4 7% 5% 5% 4 3 4 5% 31%	2934
February	1st to 10th	Day	15% 10% 3 8% 6% 5% 5% 4 6% 6% 33%	1710
	11th to 20th	Day	12% 9% 3 8% 5% 4 5% 3 5% 7% 38%	1836
	21st to end	Day	19% 9% 3 5% 6% 4 4 4 5% 6% 35%	1570
March	1st to 10th	Day	25% 10% 3 7% 4 3 3 2 3 4 33%	3116
	11th to 20th	Day	10% 8% 3 7% 5% 4 5% 4 6% 8% 41%	3315
	21st to end	Day	20% 7% 2 7% 5% 4 4 3 4 6% 38%	4152
April	1st to 10th	Day	18% 10% 4 6% 5% 3 4 3 5% 6% 36%	2280
	11th to 20th	Day	17% 7% 2 6% 5% 4 4 3 5% 6% 40%	2254
	21st to end	Day	20% 7% 2 5% 4 4 5% 3 4 5% 39%	2337
May	1st to 10th	Day	25% 8% 2 6% 4 3 4 4 5% 7% 32%	4135
	11th to 20th	Day	19% 8% 2 6% 5% 5% 4 4 5% 8% 33%	4398
	21st to end	Day	13% 4 2 5% 4 4 4 5% 6% 10% 44%	4837
June	1st to 10th	Day	16% 6% 1 6% 5% 5% 5% 4 7% 10% 35%	2660
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 4 8% 10% 36%	2660
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 6% 10% 37%	2660
July	1st to 10th	Day	9% 7% 3 8% 6% 6% 6% 4 6% 9% 37%	4440
	11th to 20th	Day	9% 6% 2 6% 4 5% 6% 5% 7% 11% 38%	4440
	21st to end	Day	12% 7% 3 8% 6% 5% 6% 4 6% 8% 34%	4814
August	1st to 10th	Day	19% 6% 3 7% 5% 5% 5% 5% 6% 8% 31%	4290
	11th to 20th	Day	12% 6% 3 7% 4 4 5% 4 8% 9% 38%	3730
	21st to end	Day	11% 5% 2 6% 5% 4 4 4 6% 10% 42%	4180
September	1st to 10th	Day	13% 7% 2 6% 4 5% 5% 4 5% 7% 43%	2280
	11th to 20th	Day	13% 5% 2 5% 3 4 4 3 6% 6% 50%	2195
	21st to end	Day	17% 6% 1 6% 4 4 5% 4 6% 7% 41%	2090
October	1st to 10th	Day	20% 6% 3 5% 4 4 3 3 4 6% 41%	1983
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 4 5% 7% 43%	1900
	21st to end	Day	22% 7% 2 6% 4 4 5% 3 5% 7% 35%	1913
November	1st to 10th	Day	13% 7% 3 6% 4 3 3 3 4 6% 47%	1698
	11th to 20th	Day	17% 8% 3 5% 4 4 4 3 5% 5% 42%	1710
	21st to end	Day	17% 9% 2 6% 4 3 4 3 5% 6% 40%	1592
December	1st to 10th	Day	19% 10% 3 7% 6% 5% 5% 4 5% 6% 31%	1520
	11th to 20th	Day	24% 7% 2 5% 3 4 3 4 5% 6% 39%	1906
	21st to end	Day	20% 11% 4 9% 6% 5% 5% 3 4 6% 28%	2772
January	1st to 10th	Night	16% 8% 3 8% 5% 4 4 3 6% 6% 39%	4429
	11th to 20th	Night	13% 9% 4 9% 6% 5% 5% 4 5% 6% 33%	4440
	21st to end	Night	24% 13% 3 7% 4 3 4 3 4 5% 31%	4720
February	1st to 10th	Night	16% 10% 3 7% 5% 4 5% 4 4 6% 37%	2470
	11th to 20th	Night	14% 9% 3 7% 5% 5% 5% 4 6% 5% 37%	2228
	21st to end	Night	18% 9% 2 7% 5% 4 4 4 5% 5% 38%	1884
March	1st to 10th	Night	24% 10% 2 6% 4 4 4 3 4 6% 33%	3724
	11th to 20th	Night	11% 9% 3 8% 5% 4 4 4 6% 6% 38%	3642
	21st to end	Night	17% 9% 3 7% 4 4 4 3 4 4 39%	3480
April	1st to 10th	Night	18% 11% 2 7% 5% 4 4 4 5% 7% 32%	1900
	11th to 20th	Night	19% 7% 3 6% 5% 3 4 4 4 7% 38%	1875
	21st to end	Night	20% 8% 2 6% 4 3 3 3 4 5% 40%	1843
May	1st to 10th	Night	26% 9% 3 6% 4 3 4 3 5% 7% 31%	2820
	11th to 20th	Night	20% 9% 3 8% 6% 3 5% 3 4 6% 33%	2495
	21st to end	Night	14% 6% 2 6% 4 4 4 4 5% 8% 41%	2738
June	1st to 10th	Night	16% 6% 1 6% 4 4 4 3 5% 8% 41%	1520
	11th to 20th	Night	15% 7% 1 5% 4 4 4 3 7% 10% 40%	1520
	21st to end	Night	13% 4 2 5% 3 5% 4 5% 8% 9% 42%	1520
July	1st to 10th	Night	11% 5% 3 6% 5% 5% 6% 5% 8% 9% 39%	2520
	11th to 20th	Night	12% 6% 2 8% 5% 4 5% 5% 7% 9% 38%	2520
	21st to end	Night	15% 8% 3 6% 5% 4 5% 3 5% 6% 40%	2739
August	1st to 10th	Night	20% 6% 2 8% 6% 5% 4 4 6% 8% 31%	2591
	11th to 20th	Night	13% 7% 3 7% 4 4 5% 4 6% 8% 38%	3097
	21st to end	Night	12% 4 2 5% 4 4 4 3 5% 8% 49%	3476
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 4 6% 46%	1900
	11th to 20th	Night	12% 5% 2 5% 3 3 3 2 5% 7% 52%	1984
	21st to end	Night	16% 6% 3 5% 3 4 4 3 5% 6% 45%	2090
October	1st to 10th	Night	21% 6% 2 7% 4 3 4 3 4 5% 40%	2194
	11th to 20th	Night	15% 7% 2 6% 5% 4 4 3 4 6% 45%	2280
	21st to end	Night	23% 7% 2 6% 4 3 3 3 5% 6% 37%	2684
November	1st to 10th	Night	14% 6% 3 6% 4 4 4 3 5% 7% 45%	2453
	11th to 20th	Night	19% 9% 2 5% 3 3 4 3 4 6% 40%	2470
	21st to end	Night	15% 7% 3 6% 4 3 4 3 6% 7% 42%	2584
December	1st to 10th	Night	20% 9% 2 7% 4 4 4 3 5% 7% 35%	2660
	11th to 20th	Night	22% 9% 3 7% 4 4 4 3 5% 6% 34%	3288
	21st to end	Night	24% 12% 3 6% 4 4 4 3 4 6% 29%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	40% 6% 13% 31% 8% 2	2518
	11th to 20th	Day	50% 7% 12% 22% 8% 2	2520
	21st to end	Day	54% 7% 10% 19% 9% 1	2934
February	1st to 10th	Day	50% 6% 12% 18% 12% 1	1710
	11th to 20th	Day	44% 6% 10% 22% 15% 3	1845
	21st to end	Day	49% 5% 11% 21% 12% 2	1570
March	1st to 10th	Day	54% 5% 10% 19% 9% 2	3119
	11th to 20th	Day	37% 9% 13% 29% 11% 2	3315
	21st to end	Day	48% 5% 7% 15% 21% 4	4152
April	1st to 10th	Day	48% 6% 9% 21% 13% 4	2280
	11th to 20th	Day	44% 5% 10% 21% 16% 3	2254
	21st to end	Day	45% 6% 9% 20% 16% 4	2337
May	1st to 10th	Day	51% 7% 12% 16% 12% 2	4149
	11th to 20th	Day	47% 9% 13% 20% 9% 1	4402
	21st to end	Day	33% 9% 13% 28% 16% 2	4837
June	1st to 10th	Day	42% 9% 14% 21% 13% 1	2660
	11th to 20th	Day	41% 8% 15% 24% 10% 2	2660
	21st to end	Day	41% 9% 13% 24% 13% 1	2660
July	1st to 10th	Day	42% 8% 13% 20% 16% 1	4370
	11th to 20th	Day	37% 9% 17% 24% 13% 1	4365
	21st to end	Day	46% 7% 13% 18% 15% 1	4661
August	1st to 10th	Day	49% 9% 13% 20% 8% 1	4276
	11th to 20th	Day	37% 9% 16% 28% 9%	3766
	21st to end	Day	36% 7% 12% 30% 13% 1	4180
September	1st to 10th	Day	39% 7% 11% 23% 17% 2	2280
	11th to 20th	Day	34% 6% 10% 25% 23% 2	2195
	21st to end	Day	40% 7% 12% 21% 17% 2	2090
October	1st to 10th	Day	40% 6% 8% 20% 23% 2	3295
	11th to 20th	Day	32% 5% 9% 27% 25% 2	3140
	21st to end	Day	33% 5% 14% 26% 18% 4	3125
November	1st to 10th	Day	37% 6% 13% 26% 16% 2	1698
	11th to 20th	Day	42% 6% 11% 21% 17% 2	1710
	21st to end	Day	44% 5% 14% 26% 9% 2	1592
December	1st to 10th	Day	53% 6% 13% 17% 10% 1	1520
	11th to 20th	Day	45% 5% 16% 22% 9% 2	1906
	21st to end	Day	54% 8% 10% 20% 7%	2772
January	1st to 10th	Night	42% 6% 13% 25% 11% 2	4429
	11th to 20th	Night	49% 6% 13% 20% 9% 3	4440
	21st to end	Night	54% 6% 10% 19% 9% 2	4720
February	1st to 10th	Night	47% 6% 14% 21% 11% 2	2470
	11th to 20th	Night	46% 7% 10% 17% 17% 3	2230
	21st to end	Night	46% 6% 9% 22% 13% 4	1884
March	1st to 10th	Night	51% 7% 10% 20% 11% 2	3734
	11th to 20th	Night	40% 9% 13% 24% 12% 2	3643
	21st to end	Night	46% 5% 7% 14% 23% 5%	3480
April	1st to 10th	Night	50% 7% 9% 19% 14% 2	1900
	11th to 20th	Night	45% 7% 9% 18% 19% 1	1875
	21st to end	Night	45% 7% 8% 21% 16% 3	1843
May	1st to 10th	Night	52% 8% 11% 17% 11% 2	2826
	11th to 20th	Night	50% 8% 12% 18% 10% 2	2496
	21st to end	Night	37% 10% 14% 24% 13% 2	2739
June	1st to 10th	Night	41% 7% 11% 24% 16% 2	1520
	11th to 20th	Night	37% 10% 15% 26% 10% 1	1520
	21st to end	Night	34% 11% 13% 27% 14% 1	1520
July	1st to 10th	Night	38% 10% 14% 20% 15% 2	2480
	11th to 20th	Night	40% 8% 14% 25% 13% 1	2472
	21st to end	Night	43% 7% 12% 19% 16% 2	2651
August	1st to 10th	Night	49% 10% 14% 18% 9% 1	2581
	11th to 20th	Night	41% 8% 15% 26% 10%	3127
	21st to end	Night	33% 7% 11% 34% 14% 1	3476
September	1st to 10th	Night	39% 7% 11% 25% 17% 1	1900
	11th to 20th	Night	32% 6% 10% 26% 25% 2	1984
	21st to end	Night	39% 7% 9% 22% 22% 1	2090
October	1st to 10th	Night	44% 6% 9% 22% 18% 1	3662
	11th to 20th	Night	30% 5% 8% 30% 26% 1	3779
	21st to end	Night	35% 5% 12% 30% 17% 1	4422
November	1st to 10th	Night	38% 7% 10% 23% 19% 3	2453
	11th to 20th	Night	45% 4 10% 22% 16% 4	2470
	21st to end	Night	41% 6% 15% 28% 10% 1	2584
December	1st to 10th	Night	48% 6% 14% 21% 11% 1	2660
	11th to 20th	Night	50% 6% 14% 16% 13% 2	3288
	21st to end	Night	53% 8% 11% 20% 9%	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	25% 19% 28% 19% 9%	180
	11th to 20th	Day	24% 23% 34% 13% 4 1	180
	21st to end	Day	20% 18% 40% 16% 5% 2	245
February	1st to 10th	Day	29% 21% 33% 14% 3	270
	11th to 20th	Day	24% 20% 37% 18% 1	444
	21st to end	Day	27% 19% 34% 17% 3	382
March	1st to 10th	Day	25% 18% 31% 22% 5%	460
	11th to 20th	Day	22% 24% 31% 18% 4 1	460
	21st to end	Day	29% 18% 28% 18% 4 3	506
April	1st to 10th	Day	29% 18% 27% 17% 6% 3	460
	11th to 20th	Day	25% 23% 27% 15% 8% 2	452
	21st to end	Day	29% 15% 29% 19% 5% 2	460
May	1st to 10th	Day	31% 15% 26% 18% 8% 2	463
	11th to 20th	Day	19% 11% 35% 23% 10% 2	487
	21st to end	Day	18% 10% 25% 30% 13% 4	529
June	1st to 10th	Day	19% 12% 27% 26% 14% 2	490
	11th to 20th	Day	14% 11% 30% 27% 16% 2	490
	21st to end	Day	15% 11% 30% 26% 15% 4	490
July	1st to 10th	Day	15% 4 26% 32% 19% 5%	485
	11th to 20th	Day	13% 5% 23% 35% 19% 5%	484
	21st to end	Day	12% 7% 28% 32% 17% 3	532
August	1st to 10th	Day	13% 7% 21% 35% 17% 7%	486
	11th to 20th	Day	14% 7% 23% 27% 21% 8%	479
	21st to end	Day	11% 7% 25% 31% 17% 9%	539
September	1st to 10th	Day	17% 11% 19% 25% 19% 8%	490
	11th to 20th	Day	14% 7% 28% 20% 18% 13%	490
	21st to end	Day	20% 9% 26% 28% 12% 6%	490
October	1st to 10th	Day	27% 10% 20% 22% 15% 6%	490
	11th to 20th	Day	17% 12% 32% 26% 10% 3	490
	21st to end	Day	26% 13% 27% 23% 9% 1	445
November	1st to 10th	Day	18% 14% 26% 30% 10% 2	374
	11th to 20th	Day	23% 15% 30% 24% 7% 1	370
	21st to end	Day	21% 15% 30% 26% 7% 1	252
December	1st to 10th	Day	23% 22% 33% 14% 8%	180
	11th to 20th	Day	27% 21% 33% 17% 2	180
	21st to end	Day	21% 14% 37% 23% 4 1	198
January	1st to 10th	Night	19% 13% 37% 28% 3	760
	11th to 20th	Night	23% 13% 35% 26% 3	760
	21st to end	Night	18% 14% 39% 25% 3	836
February	1st to 10th	Night	22% 14% 37% 26% 2	760
	11th to 20th	Night	20% 15% 43% 22% 1	743
	21st to end	Night	24% 14% 37% 22% 3	628
March	1st to 10th	Night	22% 17% 34% 24% 3	760
	11th to 20th	Night	21% 15% 38% 20% 5%	760
	21st to end	Night	22% 17% 35% 20% 6%	836
April	1st to 10th	Night	26% 14% 35% 22% 4	760
	11th to 20th	Night	22% 13% 35% 23% 7%	751
	21st to end	Night	24% 15% 29% 25% 6%	703
May	1st to 10th	Night	24% 14% 32% 24% 6%	569
	11th to 20th	Night	18% 6% 37% 34% 5%	374
	21st to end	Night	16% 7% 22% 41% 14%	411
June	1st to 10th	Night	16% 4 26% 39% 14% 1	380
	11th to 20th	Night	16% 5% 23% 38% 16% 1	380
	21st to end	Night	14% 2 25% 42% 17%	380
July	1st to 10th	Night	13% 3 18% 45% 21% 1	370
	11th to 20th	Night	13% 5% 18% 45% 18% 1	368
	21st to end	Night	12% 4 20% 44% 19% 1	416
August	1st to 10th	Night	14% 2 15% 46% 21% 2	424
	11th to 20th	Night	13% 4 16% 41% 23% 3	750
	21st to end	Night	15% 3 18% 37% 24% 3	836
September	1st to 10th	Night	18% 2 24% 36% 18% 2	760
	11th to 20th	Night	15% 4 23% 30% 23% 5%	760
	21st to end	Night	18% 6% 24% 34% 16% 2	760
October	1st to 10th	Night	24% 6% 23% 30% 14% 2	760
	11th to 20th	Night	18% 8% 29% 35% 10%	760
	21st to end	Night	26% 10% 29% 28% 7%	836
November	1st to 10th	Night	16% 10% 33% 31% 10% 1	755
	11th to 20th	Night	25% 9% 32% 25% 7% 1	760
	21st to end	Night	20% 11% 33% 29% 6% 1	760
December	1st to 10th	Night	25% 12% 34% 23% 5%	760
	11th to 20th	Night	25% 10% 34% 27% 4	760
	21st to end	Night	25% 11% 38% 23% 3	836

Page generated at 2024-11-01 22:47:47. Version ac07

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