Earl Rowe Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Earl Rowe Provincial Park clear sky chart from 2005-11-06 to 2026-01-02.

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	14% 10% 4 9% 6% 5% 5% 4 6% 7% 31%	128215
	Night	13% 11% 4 10% 6% 5% 5% 4 5% 6% 31%	123116
Transparency	Day	51% 7% 12% 19% 10% 1	131806
	Night	51% 7% 12% 19% 10% 1	127614
Seeing	Day	19% 17% 31% 20% 9% 3	16294
	Night	19% 16% 32% 24% 9% 1	25267

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	12% 11% 6% 17% 12% 6% 5% 4 5% 5% 16%	3605
	11th to 20th	Day	10% 16% 8% 19% 10% 7% 6% 4 5% 5% 11%	3930
	21st to end	Day	15% 18% 7% 16% 7% 5% 5% 4 5% 5% 14%	4466
February	1st to 10th	Day	12% 17% 4 14% 9% 6% 7% 4 5% 5% 18%	1800
	11th to 20th	Day	11% 14% 7% 14% 8% 6% 5% 4 5% 6% 20%	1753
	21st to end	Day	15% 16% 5% 12% 6% 5% 5% 3 4 5% 24%	1544
March	1st to 10th	Day	17% 11% 5% 10% 6% 5% 4 3 4 5% 29%	4925
	11th to 20th	Day	10% 14% 5% 11% 5% 5% 5% 4 5% 7% 29%	4980
	21st to end	Day	16% 15% 4 9% 5% 4 4 3 4 5% 31%	5465
April	1st to 10th	Day	15% 14% 4 9% 5% 5% 5% 3 5% 6% 30%	2345
	11th to 20th	Day	18% 12% 3 6% 4 4 3 4 5% 7% 35%	2488
	21st to end	Day	19% 11% 3 6% 5% 4 4 3 6% 5% 34%	2600
May	1st to 10th	Day	17% 9% 3 7% 5% 4 4 3 5% 7% 36%	5888
	11th to 20th	Day	15% 9% 3 8% 5% 4 4 4 5% 7% 35%	6262
	21st to end	Day	17% 7% 2 6% 4 4 4 3 5% 7% 39%	6949
June	1st to 10th	Day	15% 7% 2 6% 4 5% 5% 5% 7% 9% 36%	2800
	11th to 20th	Day	11% 6% 2 5% 5% 5% 6% 4 7% 9% 41%	2928
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 6% 9% 38%	3000
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 5% 7% 9% 38%	6786
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 4 6% 8% 46%	6360
	21st to end	Day	7% 5% 2 5% 5% 5% 5% 4 6% 8% 48%	6454
August	1st to 10th	Day	13% 7% 3 6% 4 4 5% 5% 7% 8% 38%	4234
	11th to 20th	Day	10% 6% 3 9% 5% 6% 6% 5% 7% 9% 34%	4174
	21st to end	Day	11% 5% 2 6% 5% 4 5% 4 7% 8% 43%	4543
September	1st to 10th	Day	14% 7% 2 7% 5% 5% 4 4 6% 7% 40%	2400
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	2255
	21st to end	Day	14% 7% 3 8% 6% 6% 5% 4 6% 8% 34%	2175
October	1st to 10th	Day	18% 8% 3 7% 5% 4 4 4 6% 7% 35%	2000
	11th to 20th	Day	17% 11% 4 8% 6% 5% 5% 4 6% 6% 28%	2000
	21st to end	Day	23% 16% 4 9% 5% 4 5% 3 5% 5% 22%	2200
November	1st to 10th	Day	13% 14% 4 10% 5% 5% 4 4 5% 7% 28%	1752
	11th to 20th	Day	11% 15% 4 11% 7% 7% 6% 5% 7% 7% 21%	1680
	21st to end	Day	14% 19% 6% 12% 6% 6% 5% 4 5% 6% 16%	1680
December	1st to 10th	Day	18% 19% 7% 13% 7% 6% 6% 4 5% 5% 9%	2680
	11th to 20th	Day	16% 20% 6% 13% 5% 5% 5% 4 5% 4 18%	3066
	21st to end	Day	23% 19% 7% 15% 6% 6% 4 3 4 4 10%	4048
January	1st to 10th	Night	12% 12% 6% 15% 11% 6% 5% 3 5% 6% 18%	6364
	11th to 20th	Night	11% 14% 6% 19% 11% 7% 6% 4 5% 5% 12%	5951
	21st to end	Night	13% 14% 7% 13% 8% 6% 5% 4 5% 6% 19%	6490
February	1st to 10th	Night	12% 14% 5% 13% 8% 6% 5% 4 6% 6% 21%	2600
	11th to 20th	Night	10% 14% 6% 13% 7% 6% 6% 4 5% 6% 23%	2533
	21st to end	Night	11% 13% 4 10% 8% 6% 6% 5% 5% 7% 25%	2084
March	1st to 10th	Night	15% 11% 4 10% 7% 6% 5% 4 5% 6% 27%	4913
	11th to 20th	Night	9% 10% 3 8% 5% 5% 5% 5% 6% 8% 34%	4979
	21st to end	Night	17% 10% 4 9% 5% 4 4 4 5% 6% 32%	5467
April	1st to 10th	Night	17% 12% 3 8% 5% 5% 4 4 5% 6% 30%	2054
	11th to 20th	Night	16% 9% 2 7% 5% 5% 4 4 5% 6% 38%	1877
	21st to end	Night	14% 10% 3 9% 5% 5% 5% 3 5% 6% 36%	1800
May	1st to 10th	Night	18% 8% 2 7% 4 4 5% 4 5% 7% 37%	4053
	11th to 20th	Night	13% 7% 2 7% 4 4 4 4 5% 8% 42%	3631
	21st to end	Night	17% 5% 2 5% 4 3 4 3 5% 7% 45%	3926
June	1st to 10th	Night	12% 5% 2 6% 5% 4 4 5% 6% 7% 43%	1600
	11th to 20th	Night	9% 4 2 6% 4 4 5% 5% 8% 9% 44%	1466
	21st to end	Night	11% 5% 2 6% 4 5% 4 3 7% 6% 47%	1400
July	1st to 10th	Night	6% 6% 2 7% 5% 4 4 3 6% 8% 48%	3173
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 5% 8% 51%	3600
	21st to end	Night	7% 5% 2 5% 4 4 4 3 6% 8% 52%	4381
August	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 49%	2915
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 7% 50%	2875
	21st to end	Night	11% 5% 2 5% 4 4 4 4 5% 8% 49%	3322
September	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 7% 8% 48%	2000
	11th to 20th	Night	10% 4 1 4 3 3 3 2 6% 7% 55%	2142
	21st to end	Night	16% 7% 3 7% 5% 4 4 3 4 7% 41%	2223
October	1st to 10th	Night	16% 7% 3 6% 5% 4 4 4 5% 7% 40%	2400
	11th to 20th	Night	17% 10% 3 8% 4 4 5% 4 6% 7% 34%	2400
	21st to end	Night	20% 12% 3 9% 5% 5% 5% 4 6% 5% 27%	2640
November	1st to 10th	Night	14% 11% 3 6% 5% 6% 5% 4 6% 7% 33%	2759
	11th to 20th	Night	14% 14% 5% 9% 5% 5% 5% 4 6% 7% 27%	2940
	21st to end	Night	16% 15% 6% 10% 6% 5% 6% 5% 5% 6% 20%	2940
December	1st to 10th	Night	17% 16% 7% 14% 8% 6% 5% 5% 6% 6% 12%	4720
	11th to 20th	Night	13% 18% 6% 13% 6% 6% 5% 4 5% 5% 19%	5348
	21st to end	Night	21% 20% 7% 16% 6% 5% 4 3 4 4 10%	7150

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	66% 9% 11% 12% 3	3606
	11th to 20th	Day	75% 7% 8% 6% 3 1	3964
	21st to end	Day	70% 8% 9% 9% 4	4466
February	1st to 10th	Day	68% 8% 9% 13% 3	1800
	11th to 20th	Day	64% 7% 10% 13% 5% 1	1762
	21st to end	Day	63% 5% 10% 14% 7% 1	1544
March	1st to 10th	Day	56% 6% 12% 13% 12%	4928
	11th to 20th	Day	53% 5% 14% 19% 6% 2	4980
	21st to end	Day	55% 5% 9% 19% 11% 1	5465
April	1st to 10th	Day	56% 6% 10% 18% 9% 1	2345
	11th to 20th	Day	49% 6% 9% 21% 14% 1	2488
	21st to end	Day	51% 6% 11% 18% 12% 2	2600
May	1st to 10th	Day	46% 6% 13% 18% 11% 5%	5897
	11th to 20th	Day	47% 10% 11% 15% 17% 1	6266
	21st to end	Day	44% 6% 11% 20% 15% 3	6949
June	1st to 10th	Day	41% 9% 13% 20% 15% 1	2800
	11th to 20th	Day	38% 8% 13% 24% 16% 1	2928
	21st to end	Day	41% 7% 14% 23% 13% 1	3000
July	1st to 10th	Day	41% 6% 15% 22% 14% 1	6713
	11th to 20th	Day	34% 6% 12% 31% 16% 1	6285
	21st to end	Day	33% 6% 14% 30% 16% 1	6269
August	1st to 10th	Day	43% 7% 15% 23% 12% 1	4221
	11th to 20th	Day	42% 9% 17% 22% 10%	4213
	21st to end	Day	37% 7% 13% 32% 10% 1	4543
September	1st to 10th	Day	42% 7% 14% 25% 10% 2	2400
	11th to 20th	Day	37% 7% 15% 29% 12%	2255
	21st to end	Day	47% 8% 13% 23% 9%	2175
October	1st to 10th	Day	44% 6% 12% 26% 11% 1	3260
	11th to 20th	Day	44% 6% 15% 22% 13%	3240
	21st to end	Day	60% 7% 12% 16% 6%	3538
November	1st to 10th	Day	54% 9% 14% 17% 6%	1752
	11th to 20th	Day	58% 10% 13% 12% 6% 1	1680
	21st to end	Day	68% 9% 12% 9% 2	1680
December	1st to 10th	Day	75% 6% 11% 5% 2	2680
	11th to 20th	Day	69% 8% 9% 8% 6%	3066
	21st to end	Day	79% 5% 5% 7% 4	4048
January	1st to 10th	Night	64% 8% 12% 13% 2	6364
	11th to 20th	Night	73% 9% 8% 7% 2	5992
	21st to end	Night	64% 8% 10% 10% 8% 1	6490
February	1st to 10th	Night	61% 7% 13% 15% 4	2600
	11th to 20th	Night	60% 8% 11% 16% 5%	2535
	21st to end	Night	55% 8% 14% 16% 8%	2084
March	1st to 10th	Night	56% 7% 10% 17% 9% 1	4923
	11th to 20th	Night	44% 7% 21% 19% 8% 1	4980
	21st to end	Night	51% 5% 11% 19% 12% 1	5467
April	1st to 10th	Night	54% 5% 10% 18% 11% 1	2054
	11th to 20th	Night	46% 6% 10% 20% 16% 1	1877
	21st to end	Night	48% 7% 11% 16% 16% 2	1800
May	1st to 10th	Night	46% 6% 12% 14% 14% 6%	4060
	11th to 20th	Night	40% 8% 13% 22% 15% 2	3632
	21st to end	Night	39% 7% 13% 25% 15% 2	3927
June	1st to 10th	Night	39% 8% 12% 23% 17% 2	1600
	11th to 20th	Night	34% 9% 14% 24% 18% 1	1466
	21st to end	Night	36% 8% 14% 26% 15% 1	1400
July	1st to 10th	Night	35% 5% 15% 26% 17% 2	3138
	11th to 20th	Night	32% 6% 11% 31% 18% 1	3552
	21st to end	Night	31% 6% 12% 32% 18% 1	4252
August	1st to 10th	Night	35% 6% 14% 28% 15% 1	2904
	11th to 20th	Night	34% 6% 17% 29% 13% 1	2902
	21st to end	Night	34% 6% 14% 33% 13% 1	3322
September	1st to 10th	Night	32% 8% 18% 28% 12% 1	2000
	11th to 20th	Night	28% 7% 15% 33% 17% 1	2142
	21st to end	Night	44% 6% 13% 27% 10% 1	2223
October	1st to 10th	Night	35% 6% 9% 29% 20% 1	3920
	11th to 20th	Night	42% 6% 16% 23% 13%	3899
	21st to end	Night	46% 8% 16% 22% 8%	4252
November	1st to 10th	Night	48% 9% 15% 20% 8% 1	2759
	11th to 20th	Night	55% 9% 14% 14% 7% 1	2940
	21st to end	Night	63% 10% 14% 11% 1 1	2940
December	1st to 10th	Night	71% 7% 13% 7% 2	4720
	11th to 20th	Night	67% 8% 9% 10% 6%	5348
	21st to end	Night	78% 6% 7% 7% 3	7150

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	18% 25% 35% 16% 4 1	202
	11th to 20th	Day	23% 26% 34% 12% 5% 1	278
	21st to end	Day	25% 25% 35% 13% 2	330
February	1st to 10th	Day	27% 33% 27% 10% 3	300
	11th to 20th	Day	22% 34% 37% 7% 1	300
	21st to end	Day	32% 32% 28% 8%	249
March	1st to 10th	Day	22% 23% 37% 15% 3	493
	11th to 20th	Day	21% 24% 35% 15% 5%	500
	21st to end	Day	32% 19% 29% 15% 5% 1	550
April	1st to 10th	Day	25% 24% 33% 12% 5% 1	500
	11th to 20th	Day	30% 22% 24% 14% 8% 3	492
	21st to end	Day	27% 18% 31% 16% 6% 2	500
May	1st to 10th	Day	20% 16% 35% 17% 9% 2	503
	11th to 20th	Day	18% 14% 32% 22% 10% 3	527
	21st to end	Day	17% 13% 30% 24% 12% 4	573
June	1st to 10th	Day	17% 15% 33% 24% 9% 2	530
	11th to 20th	Day	13% 13% 34% 26% 12% 2	658
	21st to end	Day	17% 13% 35% 25% 8% 3	730
July	1st to 10th	Day	10% 9% 30% 31% 15% 4	714
	11th to 20th	Day	13% 9% 29% 27% 14% 8%	524
	21st to end	Day	9% 8% 34% 31% 12% 6%	576
August	1st to 10th	Day	9% 8% 28% 30% 18% 8%	526
	11th to 20th	Day	8% 7% 28% 27% 21% 9%	519
	21st to end	Day	14% 10% 26% 26% 16% 7%	583
September	1st to 10th	Day	14% 12% 27% 23% 15% 9%	530
	11th to 20th	Day	9% 10% 22% 24% 20% 15%	530
	21st to end	Day	15% 14% 28% 22% 16% 5%	530
October	1st to 10th	Day	20% 16% 26% 20% 14% 4	530
	11th to 20th	Day	20% 23% 33% 17% 5% 2	530
	21st to end	Day	30% 21% 28% 16% 4	583
November	1st to 10th	Day	27% 25% 28% 16% 4 1	282
	11th to 20th	Day	25% 23% 35% 13% 4 1	220
	21st to end	Day	28% 24% 36% 10% 1	220
December	1st to 10th	Day	27% 26% 30% 14% 3	220
	11th to 20th	Day	29% 28% 28% 13% 1 1	220
	21st to end	Day	28% 27% 33% 10% 2 1	242
January	1st to 10th	Night	21% 26% 34% 15% 4	805
	11th to 20th	Night	22% 23% 32% 20% 4	800
	21st to end	Night	18% 18% 37% 20% 6%	880
February	1st to 10th	Night	22% 23% 37% 17% 1	800
	11th to 20th	Night	19% 23% 38% 16% 3	783
	21st to end	Night	20% 23% 35% 18% 2	660
March	1st to 10th	Night	21% 21% 36% 19% 3	800
	11th to 20th	Night	20% 24% 32% 18% 5%	800
	21st to end	Night	21% 17% 34% 21% 6%	880
April	1st to 10th	Night	24% 19% 35% 20% 2	800
	11th to 20th	Night	20% 18% 34% 19% 8% 1	693
	21st to end	Night	20% 14% 32% 25% 8%	600
May	1st to 10th	Night	17% 8% 31% 32% 11% 1	600
	11th to 20th	Night	17% 7% 35% 31% 10%	424
	21st to end	Night	10% 9% 31% 38% 12%	433
June	1st to 10th	Night	14% 7% 36% 33% 10% 1	400
	11th to 20th	Night	12% 7% 31% 38% 12%	400
	21st to end	Night	13% 7% 30% 35% 15% 1	400
July	1st to 10th	Night	6% 6% 25% 44% 18% 1	390
	11th to 20th	Night	10% 7% 28% 36% 18% 1	388
	21st to end	Night	8% 5% 28% 40% 19% 1	636
August	1st to 10th	Night	9% 4 23% 38% 25% 1	597
	11th to 20th	Night	7% 5% 20% 40% 26% 2	594
	21st to end	Night	12% 5% 28% 30% 23% 1	720
September	1st to 10th	Night	12% 7% 28% 31% 20% 4	800
	11th to 20th	Night	11% 7% 24% 29% 23% 6%	800
	21st to end	Night	19% 11% 22% 29% 17% 3	800
October	1st to 10th	Night	19% 10% 31% 24% 15% 2	800
	11th to 20th	Night	23% 15% 31% 23% 7% 1	800
	21st to end	Night	28% 16% 30% 21% 5%	880
November	1st to 10th	Night	22% 18% 31% 21% 7%	820
	11th to 20th	Night	22% 24% 30% 18% 6% 1	840
	21st to end	Night	24% 23% 33% 17% 3	840
December	1st to 10th	Night	25% 21% 36% 14% 3	840
	11th to 20th	Night	20% 25% 37% 16% 3	840
	21st to end	Night	30% 18% 34% 16% 2	924

Page generated at 2025-12-30 01:14:07. Version ac07

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